KR100675885B1 - Method of inspecting wafer using e-beam - Google Patents

Abstract

The wafer inspection method using the electron beam of the present invention is a method in which the electron beam is irradiated onto the wafer to indicate whether the wafer is defective or not by the contrast of the displayed image. In the wafer inspection method using the electron beam according to the present invention, the brightness level of the inspection target region of the wafer is limited to the class corresponding to 1/2 of the darkest to the brightest, and thus the lowest peak signal of the contrast signal of the image. Irradiating an electron beam to the wafer under a set condition such that the peak peak signal is included in the limited class and the peak peak outside the limited class, detecting the secondary electrons generated from the wafer, and analyzing the detected secondary electrons. And converting the analysis result into data to display whether or not a defect exists in the wafer as an image.

Electron Beam, Wafer Inspection, Image Training, Image Brightness Rating, Gain Shape

Description

Method of inspecting wafer using e-beam

1 is a graph shown to explain inspection conditions used in a wafer inspection method using a conventional electron beam.

FIG. 2 is a diagram illustrating image training displayed as an inspection result according to the inspection condition of FIG. 1.

Figure 3 is a graph shown to explain the inspection conditions used in the wafer inspection method using an electron beam according to the present invention.

FIG. 4 is a diagram illustrating image training displayed as an inspection result according to the inspection condition of FIG. 3.

FIG. 5 is a diagram illustrating a result of a test performed by a wafer inspection method using an electron beam according to an embodiment of the present invention and a test performed after an actual process is performed.

The present invention relates to a wafer inspection method, and more particularly, to a wafer inspection method using an electron beam.

In general, the wafer is inspected using various inspection methods to confirm that the process is properly performed during the manufacturing of the semiconductor device. Among such inspection methods, a wafer inspection method using an electron beam (E-beam) is used to inspect a contact. Typically, a wafer inspection method using an electron beam is performed through an electron beam inspection equipment.

The wafer inspection method using this electron beam can be performed in the following three process steps. The first is to check whether the contact hole is sufficiently open after forming the contact hole, for example, after forming the contact hole for the landing plug, the contact hole for the storage node, or the contact hole for the metal wiring. Secondly, after the contact hole is formed, the contact hole is filled with a conductive material. In this case, it is necessary to check whether the contact hole is incompletely etched and whether there is a microdefect of the lower pattern or the lower junction. will be. The third is after patterning the conductive film on the upper part of the contact, in this case, to check for the presence of residues or stringers between the patterns made.

In the first and third cases, only one type of defect can be detected, whereas in the second case, several types of defects can be detected at one time. Thus, the most effective inspection method is the second case. Can be. In this case, however, if the wafer is positively charged by the electron beam inspection equipment, the reverse bias is applied to the pn junction by the conductive material and the substrate junction that fills the contact hole, resulting in uneven leakage current at each junction. Is generated. In this way, when the leakage current amount at each junction is unevenly generated, it is difficult to distinguish between the actual defect and the defect caused by the nonuniformity of the leakage current amount in the image training showing the inspection result, and as a result, it is easy to selectively detect only the actual defect. Not.

1 is a graph shown to explain inspection conditions used in a wafer inspection method using a conventional electron beam. FIG. 2 is a diagram illustrating a result of inspection performed by the inspection condition of FIG. 1. In FIG. 1, the horizontal axis represents the brightness level of the inspection target region in the wafer, and the vertical axis represents the signal intensity.

First, referring to FIG. 1, in a conventional wafer inspection method using an electron beam, a gain type is set to a normal gain. Here, the normal gain refers to a condition in which the contrast level can be adjusted to a different value optimized for each region to be examined in adjusting the gain for the contrast of the image representing the inspection result. In addition, the brightness class condition of the inspection area was limited to 50-200. Typically, the overall brightness class is divided into 256 classes. In this case, both the lowest peak signal 110 and the shortest peak signal 120 are included in the brightness class.

As a result of the image training, as shown in Fig. 2, in addition to the actual defects, defects due to the nonuniformity of the leakage current appear together, and in particular, it is difficult to distinguish between the two defects. Specifically, as shown in the left figure of FIG. 2, the presence or absence of defects in the inspected wafer 200 is indicated by contrast, and the black portion is a portion that is indicated as defective. In addition, as shown in the diagram on the right of FIG. 2, a defective part is displayed as a bright part in the displayed image. By the way, the part indicated as defective as a result of the inspection includes a defect due to the nonuniformity of the leakage current, in addition to the actual defect, there is a problem that it is not easy to distinguish between the two defects as mentioned above.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a wafer inspection method using an electron beam capable of selectively and accurately detecting only actual defects.

In order to achieve the above technical problem, a wafer inspection method using an electron beam according to the present invention, in the wafer inspection method using an electron beam in which the electron beam is irradiated to the wafer to indicate whether the wafer is defective or not represented by the contrast of the image, The brightness class of the inspection target region is limited to the class corresponding to 1/2 of the darkest to the brightest class so that the lowest peak signal of the contrast signal of the image is included in the limited class and the highest peak signal is the limited class. Irradiating the electron beam onto the wafer under a set condition to be included outside; Detecting secondary electrons generated from the wafer; And analyzing the detected secondary electrons and converting the result into data to display whether or not a defect exists in the wafer as an image.

In the present invention, the gain type for adjusting the gain of the contrast of the image can be set to a linear gain condition for adjusting the gain to a uniform value over the entire inspection target region of the wafer.

The brightness grade of the inspection target region of the wafer may be 1-120 grade.

The wafer may include an insulating layer disposed on the lower layer on the wafer, and a conductive contact electrically connected to the lower layer through the insulating layer.

In this case, the conductive contact may be a polysilicon film in which impurities inside are activated.

Impurity activation of the polysilicon film may be performed using annealing or rapid heat treatment in the furnace.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below.

First, in the wafer inspection method using the electron beam according to the present invention, the wafer is loaded onto the wafer inspection equipment using the electron beam, and the electron beam is irradiated onto the wafer while the wafer inspection equipment is set at a predetermined condition. Then, secondary electrons are generated on the wafer surface by the electron beam, and after detecting the secondary electrons, the detected secondary electrons are data to indicate whether the wafer is defective as a contrast of the image. In this case, a contact hole penetrating through the insulating film on a predetermined lower layer is formed in the wafer, or a conductive contact is formed in the contact hole, and a material film on the upper portion of the conductive contact is patterned. It may be a later state. The most preferable case is the second case, wherein an impurity activated polysilicon film is used as the conductive film constituting the conductive contact. Impurity activation of this polysilicon film can be carried out through an annealing process made in a conventional furnace. Or, in some cases, may be performed through a Rapid Temperature Process (RTP).

Figure 3 is a graph shown to explain the inspection conditions used in the wafer inspection method using an electron beam according to the present invention. In FIG. 3, the horizontal axis represents the brightness level of the inspection target region in the wafer, and the vertical axis represents the signal intensity.

Referring to FIG. 3, in inspecting a wafer by using an electron beam according to an embodiment of the present invention, as an inspection condition of a wafer inspection apparatus, the brightness grade of the inspection target region of the wafer is from the darkest to the brightest grade. Use the setting conditions limited to class 2. That is, the brightness grade of the inspection target area of the wafer is classified into grades 1 to 255, and is limited to approximately 120-130 grades, which is half the level of the brightest grade, which is the most obtained grade. Then, the lowest peak signal 310 of the image contrast signal is included in a limited class, for example, within the range of 1 to 120 grades, and the highest peak signal 320 of the image contrast signal is outside the range of 1 grade to 120 grades. do. That is, the overall darkened image training results can be obtained. Accordingly, only defect indications due to actual defects can be selectively obtained, rather than defects due to nonuniformity of leakage current.

In addition, in the wafer inspection method using the electron beam according to the present invention, a linear gain condition is used as a gain type for adjusting the gain of the contrast of the image. Herein, the linear gain condition means a condition for controlling gain to a uniform value over the entire inspection target region of the wafer. That is, it is a condition for adjusting gain in the form of darkening or brightening uniformly.

FIG. 4 is a diagram illustrating a result of inspection performed by the inspection condition of FIG. 3. 4 shows the image training of the wafer by the wafer inspection method using the electron beam according to the present invention, and the right figure shows the image showing the portion marked as a defect in the image training.

Referring to FIG. 4, it can be seen that a large portion of the wafer 400 is displayed brightly, whereas a large portion of the dark colored portion appears mainly at the edge of the wafer 400. This means that actual defects in the wafer 400 mainly exist at the edge of the wafer 400. Comparing the distribution of light and shade shown in Fig. 4 with Fig. 2 showing the results performed by the conventional inspection method, it can be clearly seen that only actual defects appear selectively.

FIG. 5 is a diagram illustrating a result of a test performed by a wafer inspection method using an electron beam according to an embodiment of the present invention and a test performed after an actual process is performed.

Referring to FIG. 5, a dark portion showing the actual defect of the wafer 500 after the actual process is performed, and the image training resulting from the wafer inspection method using the electron beam according to the present invention as shown in FIG. 4. You can see that the results are almost identical.

As described so far, according to the wafer inspection method using the electron beam according to the present invention, the inspection using the electron beam is performed with the brightness level of the inspection target region being approximately 1-120 and the gain form set to the linear form. As a result, the display by the actual defect is made clear rather than the defect due to the nonuniformity of the leakage current, and thus, it is possible not only to accurately determine whether the process is defective, but also to provide an advantage of setting the expected yield more accurately.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the technical spirit of the present invention. Do. For example, in some cases, the gain type may be set to normal gain, and even if the inspection target area is set to about 1-120, the peak signal may be included in the setting range.

Claims (6)

In the wafer inspection method using an electron beam by irradiating the electron beam to the wafer to indicate whether the defect of the wafer in the contrast of the displayed image, The brightness grade of the inspection target region of the wafer is limited to the class corresponding to 1/2 of the darkest to the brightest grade, so that the lowest peak signal of the contrast signal of the image is included within the limited grade and the highest. Irradiating the wafer with the electron beam under a set condition such that a peak signal is outside the defined class; Detecting secondary electrons generated from the wafer; And Analyzing the detected secondary electrons and converting the result into data to display whether or not a defect exists in the wafer as an image. The method of claim 1, A gain type for adjusting the gain of the contrast of the image is set to a linear gain condition for adjusting the gain to a uniform value over the entire inspection target area of the wafer. Wafer inspection method. The method of claim 1, Wafer inspection method using an electron beam, characterized in that the brightness grade of the inspection target region of the wafer is 1-120 grade. The method of claim 1, wherein the wafer, An insulating film disposed on the lower film on the wafer; And And a conductive contact electrically connected to the lower layer through the insulating layer. The method of claim 4, wherein The conductive contact is a wafer inspection method using an electron beam, characterized in that the impurity is activated polysilicon film. The method of claim 5, Impurity activation of the polysilicon film is carried out using annealing or rapid heat treatment in the furnace using an electron beam wafer inspection method.

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