KR101301430B1 - Defect mesurement method for a wafer - Google Patents

Abstract

In order to find out the defect density that can represent the wafer with high reliability, the defect density of at least one specific point of a certain wafer is obtained by a visual information acquisition method, and the predetermined range including at least the specific point by the half width measurement method of XRD. Measuring half width of; Obtaining a correlation between the defect density by the visual information acquisition method and the half width of the XRD half width measurement method; And determining a defect density of the wafer using the half width based on the correlation.

Description

DEFECT MESUREMENT METHOD FOR A WAFER

The present invention relates to a method of measuring the binding of a wafer.

Gallium nitride is a material mainly used as a light emitting device. The luminous efficiency of the light emitting device has a close influence on the crystallinity of the gallium nitride wafer, and this crystallinity is greatly influenced by the defect density exemplified by the threading dislocation density (TDD) present in the gallium nitride wafer. Therefore, it is important to control the penetration potential during the growth of gallium nitride wafers, and furthermore, the extent to which such defects are present is treated as a major index indicating the performance and characteristics of gallium nitride wafers. The consumer of gallium nitride wafers treats the number of defects or the density of defects as major indicators and requires the gallium nitride wafer producers to present them in detail.

In general, a method for measuring defects of a gallium nitride wafer is represented by density by counting the number of defects that appear after photographing a surface of a gallium nitride wafer with an imaging device such as an atomic force microscope (AFM), or a transmission electron microscope (TEM). After fabrication of the specimen, the density is calculated by counting the number of defects in the image after measuring the image. This method can be called a visual information acquisition method obtained by capturing a small area and counting the number of defects in the photographed image.

However, as described above, the method of determining the defect density by counting the number of defects among the images acquired through the microscopic image shooting has a large error when the contrast difference of the image is large and it is difficult to accurately determine the number of defects. There is a problem. In addition, since the measurement area is very narrow in micrometers, a large error may occur when representing a representative value of the entire wafer. In addition, since many wafers show large differences in dislocation densities in images of several micrometers, there is a problem that a large difference may occur depending on the measurement position. In addition, there is a disadvantage in that a lot of time is taken to take an image and a lot of cost is required.

SUMMARY OF THE INVENTION The present invention is proposed in the background of the above-described problems, and an object of the present invention is to find a defect density in a short time and a small cost, and to provide a defect measuring method of a wafer which can more accurately represent the defect density over the entire area of the wafer. It is done.

In the defect measuring method according to the present invention, the defect density of at least one specific point of a certain wafer is obtained by a visual information acquisition method, and the half width of a predetermined range including at least the specific point is measured by the half-width measuring method of XRD. that; Obtaining a correlation between the defect density by the visual information acquisition method and the half width of the XRD half width measurement method; And calculating the defect density of the wafer using the half width based on the correlation.

According to another aspect of the present invention, there is provided a defect measuring method comprising: obtaining a correlation between a defect density by a visual information acquisition method and a half width of a half-width measurement method of an XRD; And determining the grade of the wafer by comparing the half width that can represent a certain wafer with a predetermined threshold based on the correlation.

According to another aspect of the present invention, there is provided a defect measuring method comprising: obtaining a correlation between a defect density by a visual information acquisition method and a half width of a half width measurement method of an XRD; And measuring the half width of a certain wafer, and calculating a defect density of the wafer based on the correlation, wherein the correlation is continuously used when measuring a defect of a wafer that has passed the same manufacturing conditions. .

In another aspect, the defect measuring method according to the present invention is based on the correlation between the half width and the defect density, and the half density of the wafer is measured by the half width measurement method of the XRD to determine the defect density of the wafer. It is characterized by finding out.

According to the present invention, by using the X-ray diffraction method that can be obtained with little time, cost and effort, there is an advantage that the defect density of the wafer can be more accurately found as a representative value for the entire area of the wafer.

1 is an image obtained by the visual information acquisition method.
2 is a half width contour line obtained by the XRD method.
3 is a correlation graph of the half width obtained by the visual information acquisition method and the XRD method.
4 is a flowchart of a defect measurement method of a wafer according to the first embodiment;
5 is a flowchart of a defect measurement method of a wafer according to the second embodiment;
6 is a flowchart of a defect measurement method of a wafer according to the third embodiment;

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, the spirit of the present invention is not limited to the accompanying embodiments, and those skilled in the art who understand the spirit of the present invention can easily add, change, delete, and add other embodiments included in the scope of the same idea. It may be proposed, but this can also be said to fall within the scope of the present invention.

≪ Embodiment 1 >

When X-rays are tightened on a gallium nitride wafer, the X-ray diffraction angle on a specific surface is determined according to the crystal characteristics of gallium nitride. In this case, if the crystallinity is perfect, the diffracted X-ray becomes a single line, but if there is a defect in the crystal of the wafer, the intensity of the diffracted X-ray shows a Gaussian distribution instead of a single line, which is called a rocking curve. do. The full width (FWHM) of the rocking curve has a unit of arcsec. When the half width of the locking curve is large, it can be understood that many crystal defects exist.

However, when the X-ray diffraction method (XRD) is used, it is possible to know how many defects exist as the half width of the rocking curve, but there is a problem in that the defect density and the number of defects are not known. Particularly, the half width of the locking curve is changed even in the case of the same number of defects and the density of defects, depending on various factors such as the base material of gallium nitride, growth conditions of gallium nitride, crystal characteristics, growth apparatus, and the like. The accuracy of the defect density has a problem that can not be secured more and more.

Due to this problem, the XRD method has not been applied in measuring the defect density and the number of defects of a gallium nitride wafer. However, the inventors of the present invention further study the method of measuring the defect density and the number of defects using the XRD method due to the advantages of the rapid and inexpensive measurement method and the rapid measurement of a large area. It came to invention.

On the other hand, in the case of a gallium nitride wafer, a defect leading to the present invention is used as a light emitting device, so a threading dislocation density (TDD) may be exemplified. In addition, as the gallium nitride wafer, a wafer in which gallium nitride is epitaxy on a silicon substrate may be preferably applied.

The inventors first tried to verify the correlation between the defect density measured by the visual information acquisition method and the half width obtained by the XRD method.

FIG. 1 illustrates a method of acquiring a visual information, and a 2 micrometer range is photographed on a gallium nitride wafer using AFM, and it is a defect that is displayed as a dot among the images. Fig. 2 shows contour lines connected to each other where the half widths measured by tightening the x-rays of 0.04 mm × 8 mm at 36 points at 0.1 mm intervals show the same values. The XRD method is measured along the (102) plane where various dislocations affect both X-ray diffraction.

A graph showing a correlation with the number of defects measured by the visual information acquisition method shown in FIG. 1 at a specific point on the contour line shown in FIG. 2 is shown in FIG. 3.

Referring to FIG. 3, the red dot represents the number of defects measured by the visual information acquisition method at a specific point, and the graph shows the half width of each point of the wafer measured by the visual information acquisition method from the contour line shown in FIG. 2. . According to FIG. 3, it can be seen that the number of defects and the half width are exactly proportional to each other. Therefore, when the half width value is obtained on a certain point of the wafer by the XRD method, and the number of defects or the density of the defects are measured by the visual information acquisition method at a specific point where the half width is measured, the half width and the visual by the XRD method are measured. The correlation of defect density by information acquisition method can be utilized. That is, when the defect density obtained by the visual information acquisition method obtained at a certain point is 1 cm ^-2 and the half width of the XRD method at that point is 700 arcsec, the defect density on the entire surface of the wafer is 700: 1. Corresponding to the half-width measured by.

In this way, the visual information acquisition method for any one point can correspond to the half width of the XRD method for the entire surface, so that it is possible to obtain the advantage of finding out more accurately the density of defects corresponding to the entire surface of the wafer. do.

Of course, the correlation between the half width of the XRD and the defect density of the visual information acquisition method may be different in various cases such as a base material of gallium nitride, growth conditions of gallium nitride, crystal properties, and growth apparatus. Therefore, if any of the above conditions change, it is necessary to newly measure the correlation.

4 is a defect measurement method of a wafer according to a first embodiment using a visual information acquisition method and a XRD half width measurement method.

Referring to FIG. 4, as a visual information acquisition method, a specific point is photographed (S11), and a defect density is measured in an image of the photographed specific point (S12). Apart from the visual information acquisition method, the X-ray diffraction apparatus is operated using the XRD method (S21), and the full width is measured (S22).

In this case, the measurement of the half width is preferably performed over a predetermined range of the wafer. This is because a defect density value of a wafer that can substantially represent a particular wafer can be obtained only when the defect density of the wafer over a predetermined range is confirmed. It can be said that the half width of a certain range or more is measured depending on the precision.

Thereafter, as shown in the description of FIG. 3, the defect density at a specific point obtained through the visual information acquisition method and the half-width at the specific point are correlated to how much the defect density is. Acquire a relationship. By using the correlation, if the defect density is obtained by enlarging the entire region of the wafer whose half width is measured, the defect density representative of the wafer can be found (S30).

If it is difficult to find the defect density by only one point, the defect density may be obtained from two or more points, and a more accurate correlation may be used.

The wafer defect measuring method according to the first embodiment can be expected to be used in finding the correct defect density for any one wafer. However, since the XRD method should always be performed over a certain range and the defect density should be obtained by visual information acquisition method, although a value representative of the entire wafer area may be obtained, It is true that there is a problem that takes too much time to measure defects.

≪ Embodiment 2 >

As one method of evaluating a wafer, certain thresholds for defects may be established and the wafer may be graded. As a simple example, it is possible to distinguish between usable and unusable articles, so that if the defect is greater than or equal to the threshold, the wafer class cannot be used. If the defect is less than or equal to the threshold, the wafer class can be used. Of course, if you set multiple thresholds, you might be able to determine the grade of the wafer.

5 is a flowchart of a defect measurement method of a wafer according to a second embodiment.

Referring to FIG. 5, the visual information acquisition method and the half width measurement method of the XRD are performed in the same flow as that performed in the first embodiment (S11, S12, S21, and S22). Thereafter, a correlation may be derived (S40), and the grade of the wafer may be determined using the full width based on the derived correlation.

As an example, by comparing the half-width and a predetermined threshold (S41), if the half-width is larger it can be determined as bad (S43), if the half-width is not larger can be determined to be good (S42). The half width may be converted into a defect density (cm ⁻² ), and likewise, the threshold may be a value of a threshold for the defect density. On the contrary, the half width may have a unit of an arc sec, and if so, the threshold may be converted into an angle value. It can be easily estimated that this can be done by the correlation between the visual information acquisition method and the XRD half-width measurement method.

Here, the half width compared with the threshold may be an average half width of the full range measured by the XRD method, or may be the highest value among the full ranges measured by the XRD method. Of course, various other conditions may be given depending on the needs of the wafer.

In the description of the second embodiment, overlapping portions are used for the description of the first embodiment, and the description thereof is omitted, but the description of the first embodiment may be applied as it is.

According to the second embodiment, it is possible to increase the speed of the work time because only the job of determining the grade and whether the good or bad. Such a problem can be said to be difficult to calculate accurate data.

≪ Third Embodiment >

Since the third embodiment is based on the first and second embodiments, the descriptions of the first and second embodiments are used for the parts without specific description. In the third embodiment, as in the first and second embodiments, the visual information acquisition method and the half width measurement method of the XRD are performed.

On the other hand, as already mentioned in the description of the first embodiment, when manufacturing a wafer, a wafer and a buffer layer on which a single crystal material is grown, growth conditions, crystal characteristics, specifications of a growth apparatus, and the like are manufactured on the wafer. As for the correlation between the visual information acquisition method and the XRD half width measurement method, the correlation is the same. By using this property, after performing one correlation matching, the same correlation will be used for the next inspection, so that the defect density can be determined by finding only the half width by the XRD method. However, if any one of the conditions is different, it will be easily guessed that a correlation between the visual information acquisition method and the XRD half-width measurement method should be newly created.

6 is a flowchart of a defect measurement method of a wafer according to the third embodiment.

Referring to FIG. 6, the visual information acquisition method and the half width measurement method of the XRD are performed in the same flow as those performed in the first and second embodiments (S11, S12, S21, and S22). After that, the correlation is derived and the defect density is calculated (S40). This process can be regarded as the same as the correlation derivation and the defect density calculation (S30) of the first embodiment.

Subsequently, a return is performed to introduce a new wafer (S51), and the half width of the newly received wafer is measured for a region over a predetermined range (S52). Then, using the half width obtained in the half width measurement step (S52), the defect density is calculated based on the correlation obtained in the correlation derivation and the defect density calculation step (S50) (S53). If there is a wafer to be newly inserted, the process proceeds to the step of introducing a new wafer (S51).

This embodiment is limited to a wafer manufactured under the same conditions, and when the wafer manufacturing conditions are different, a new correlation between the visual information acquisition method and the XRD half-width measurement method is obtained, and the newly obtained correlation is used to determine the defect. It will be easy to guess the density.

In the present embodiment, when manufacturing a wafer, the wafer and the buffer layer on which a single crystal material is grown, the growth conditions, the crystal characteristics, the specifications of the growth apparatus, and the like are the same. The correlation between the measurement methods is the same. Thus, in the case of a wafer manufactured under the same manufacturing conditions, the visual information acquisition method can obtain sufficient advantages in one operation.

In addition, it is obvious that if the experiments already conducted have a correlation in advance based on the results, all the processes of the defect measurement method can be terminated only by the half width measurement (S52) and the defect density calculation (S53). will be.

According to the present invention, it is possible to find out the defect density of the wafer with high reliability. In addition, the X-ray diffraction method has an advantage of finding out the defect density more accurately as a substantial representative value of the wafer.

Claims (7)

Obtain a defect density of at least one specific point of the wafer by visual information acquisition method,
Measuring a half-width of a predetermined range including at least the specific point by a half-width measuring method of XRD;
Obtaining a correlation between the defect density by the visual information acquisition method and the half width of the XRD half width measurement method; And
Calculating a defect density of the wafer using the half width based on the correlation. The method of claim 1,
Wherein the defect density is a penetration potential density, and the wafer is a gallium nitride wafer having gallium nitride epitaxially bonded to a silicon substrate. The method of claim 1,
And a region measured by the half width measurement method of the XRD larger than the region measured by the visual information acquisition method. Determining the correlation between the defect density by the visual information acquisition method and the half width of the XRD half width measurement method; And
And determining a grade of the wafer by comparing a half width that can represent the wafer and a predetermined threshold value based on the correlation. Determining the correlation between the defect density by the visual information acquisition method and the half width of the XRD half width measurement method; And
Measuring the half width of the wafer and calculating the defect density of the wafer based on the correlation;
A method for measuring a defect of a wafer, wherein the correlation is continuously used when measuring a defect of a wafer that has passed the same manufacturing conditions. Based on the correlation between the half width and the defect density,
A wafer defect measuring method for determining a defect density of a wafer by measuring a half width of a predetermined range of a wafer by a half width measuring method of XRD. The method according to claim 6,
The correlation is a defect measurement method of the same wafer for the wafer that passed the same manufacturing conditions.

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