Electron beam inspection apparatus and method for testing an operation state of an electron beam inspection apparatus

In a method for testing an operation state of an electron beam inspection apparatus, an electron beam sequentially scans a plurality of scan lines in a predetermined inspection area on a substrate. A detector detects secondary electrons emitted from the scan lines and an image acquisition unit acquires inspection images corresponding to the scan lines from the secondary electrons. An image processing unit analyzes the inspection images using an initial sensitivity in order to detect defects on the scan lines. A graphic unit produces an inspection graph indicating the number of defects and an operation unit compares the inspection graph with a reference graph. A compensator compensates a sensitivity difference corresponding to a difference between the inspection graph and the reference graph.

FIELD OF THE INVENTION

Embodiments of the present invention relate to an electron beam inspection apparatus. In embodiments, an electron beam inspection apparatus detects defects on a substrate using an electron beam and a method tests the operation state of the electron beam inspection apparatus.

The present application claims priority from Korean Patent Application No. 2003-42241, filed Jun. 26, 2003, the disclosure of which is incorporated herein by reference in its entirety.

DESCRIPTION OF THE RELATED ART

Semiconductor devices may be manufactured through a three-step process. In a first step, a fabrication process is performed for forming electronic circuits on a silicon wafer (i.e. a semiconductor substrate). In a second step, an electrical die sorting (EDS) process is performed for inspecting electrical characteristics of the semiconductor devices formed on the semiconductor substrate in the fabrication process. In a third step, a packaging process is performed for packaging the semiconductor devices in epoxy resins and individuating the semiconductor devices.

The fabrication process may include various unit processes. Examples of the unit processes are a deposition process, a photolithography process, an etching process, a chemical mechanical polishing process, an ion implantation process, a cleaning process, and an inspection process.

The inspection process may be performed to detect defects such as scratches, particles and residue remaining on the semiconductor substrate in a layer, or unintentional patterns formed on the semiconductor substrate. The defects deteriorate the performance of the semiconductor devices as well as lower production yield in manufacturing the semiconductor devices.

Various inspection apparatuses may be employed in the inspection process. Examples of various inspection apparatuses are secondary ion mass spectrometry using an ion beam, a surface inspection apparatus using a laser beam, and an inspection apparatus using an electron beam (e.g. scanning electron microscope, a transmission electron microscope, and an electron beam inspection apparatus).

U.S. Pat. No. 5,917,588 to Addiego discloses an automated specimen inspection system and a method of distinguishing features or anomalies under either bright field or dark field illumination. U.S. Pat. No. 6,215,551 to Nikoonahad et al. discloses a scanning system for inspecting anomalies on surfaces. The scanning system directs a focused beam of light at a grazing angle towards the surface to be inspected and detects the anomalies by collecting the light scattered form the surface of a wafer. U.S. Pat. No. 6,407,373 to Dotan discloses an apparatus and method for reviewing defects on an object using an optical microscope and a scanning electron microscope (SEM). U.S. Pat. No. 6,265,719 to Yamazaki et al. discloses an inspection method and apparatus using an electron beam.

The electron beam inspection apparatus may include an electron beam source, a stage, a driving unit, a detector, an image acquisition unit, an image processing unit, and a display unit. The electron beam source can generate an electron beam. The stage can support a substrate (e.g. a silicon wafer). The driving unit can adjust a position of the stage. The detector can detect secondary electrons emitted from a predetermined inspection area on the substrate. The image acquisition unit can acquire an inspection image from the detected secondary electrons. The image processing unit can analyze the inspection image to detect defects existing in the inspection area. The display unit can display the inspection image.

The electron beam source may include an electron gun for generating electrons and a column having a magnetic lens unit. The magnetic lens unit extracts the electrons to form the electron beam and controls an advancing direction of the electron beam. The electron gun includes a filament for emitting the electrons and an extraction electrode for extracting the electrons. The electrons extracted through the extraction electrode are irradiated onto the inspection area of the substrate through the magnetic lens unit. The magnetic lens unit includes a pair of condenser lenses for condensing the extracted electrons to form the electron beam and an objective lens for adjusting a spot size of the electron beam irradiated onto the inspection area of the substrate.

The electron beam formed by the condenser lens is deflected by a scan coil disposed between the pair of condenser lenses and the objective lens. The deflected electron beam scans the inspection area of the substrate through the objective lens. The intensity and spot size of the electron beam may be adjusted by an electric field strength and a magnetic field strength formed by the magnetic lens unit.

The electric field strength and the magnetic field strength may vary with time. Variations of the electric field strength and the magnetic field strength may cause a change in optical characteristics of an electron beam. As a result, a detection rate of defects may deteriorate.

A process for testing an operation state of the electron beam apparatus is periodically performed to prevent the detection rate of the defects from deteriorating. A reference substrate having a predetermined number of defects is used in the testing process for the electron beam inspection apparatus. The number of defects detected from the reference substrate by the electron beam inspection apparatus is compared with the predetermined number. When a difference between the number of the detected defects and the predetermined number exceeds a predetermined tolerance range, a sensitivity used in an image analysis step may be adjusted or the electric field strength and the magnetic field strength may be adjusted.

The inspection process on the reference substrate should be performed more than once in order to confirm that a normal defect detection rate has been restored after adjustment of the sensitivity, the electric field strength, and/or the magnetic field strength. However, it is difficult to successively perform the inspection process on the same reference substrate because of charging effects generated by irradiation of the electron beam. The time required for removing the charging effects of the reference substrate lowers throughput of the electron beam inspection apparatus. In addition, to confirm whether or not the sensitivity, the electric field strength, and/or the magnetic field strength has been correctly adjusted, the inspection process should be repeatedly performed from a few times to dozens of times.

An amount of the secondary electrons emitted along a plurality of scan lines or a plurality of scan swaths in the inspection area of the substrate may be varied in accordance with the plurality of scan lines. Thus, it is difficult to judge the operation state of the electron beam inspection apparatus from only the amount of the secondary electrons. It is necessary to repeatedly perform the electron beam inspection process on the reference substrate in order to ensure operational reliability of the electron beam inspection apparatus. Accordingly, during this recalibration, the time required for testing the operation state of the electron beam inspection apparatus may be increased and the throughput of the electron beam inspection apparatus may be decreased.

SUMMARY OF THE INVENTION

Embodiments of the present invention relate to a method for testing an operation state of an electron beam inspection apparatus using an inspection graph that indicates the number of defects existing on a substrate and a reference graph. Embodiments also provide an electron beam inspection apparatus for performing the testing method.

According to embodiments of the present invention, a method for testing the operation state of an electron beam inspection apparatus comprises sequentially scanning a plurality of scan lines in a predetermined inspection area on a substrate with an electron beam, detecting secondary electrons emitted from the scan lines, acquiring inspection images corresponding to the scan lines from the detected secondary electrons, analyzing the inspection images using an initial sensitivity to produce an inspection graph indicating the number of defects on the scan lines, and comparing the inspection graph with a reference graph.

The defects may be detected by comparing gray levels of pixels with one another, each pixel representing a part of the inspection images. The reference graph may be produced by analyzing experimental images acquired from a reference substrate using a reference sensitivity. The initial sensitivity may be substantially identical to the reference sensitivity. When the difference between the inspection graph and the reference graph exceeds a predetermined tolerance range, the initial sensitivity may be adjusted so that the difference is within the tolerance range.

The reference graph may be acquired by performing the following steps: Scanning a plurality of scan lines sequentially in a predetermined experimental area on a reference substrate using the electron beam. Detecting secondary electrons emitted from the scan lines in the experimental area. Acquiring experimental images from the detected secondary electrons in the experimental area. Analyzing the experimental images using an experimental sensitivity so as to produce an experimental graph indicating the number of defects on the scan lines in the experimental area. Repeatedly analyzing the experimental images while the experimental sensitivity is gradually increased or decreased. Selecting the reference graph from a plurality of experimental graphs produced by repeatedly analyzing the experimental images.

According to embodiments of the present invention, a step of comparing an inspection graph with a reference graph may be performed by comparing an inspection graph area with a reference graph area. Areas of the experimental graphs including the reference graph are calculated. The inspection graph area is calculated. The calculated inspection graph area is compared with the reference graph area referring to an area variation graph, showing an area variation of the experimental graphs. The initial sensitivity may be adjusted in accordance with a sensitivity difference corresponding to a difference in value between the inspection graph area and the reference graph area. The area variation graph may be expressed by a functional equation (e.g. a simple equation or a quadratic equation). The sensitivity difference may be obtained from the functional equation.

The electron beam inspection apparatus for performing the testing method may comprise an electron beam source, a stage, a driving unit, a detector, an image acquisition unit, an image processing unit, a graphic unit, and/or an operation unit. The electron beam source can generate an electron beam and control an advancing direction of the electron beam so that the electron beam scans a plurality of scan lines sequentially in a predetermined inspection area on a substrate. The stage can support the substrate. The driving unit can adjust a position of the stage such that the electron beam is irradiated onto a surface of the inspection area. The detector can detect secondary electrons emitted from the scan lines. The image acquisition unit, connected to the detector, can acquire a plurality of inspection images corresponding to the scan lines from the detected secondary electrons. The image processing unit can analyze the inspection images using an initial sensitivity in order to detect defects on the scan lines. The graphic unit can produce an inspection graph indicating the number of detected defects on the scan lines. The operation unit can compare the inspection graph with a reference graph.

The operation unit may include a first operator, a comparator, and a second operator. The first operator can calculate areas of the experimental graphs, a reference graph area, and an inspection graph area. The comparator can compare the inspection graph area with the reference graph area. The second operator can determine a sensitivity difference corresponding to a difference in value between the inspection graph area and the reference graph area.

The electron beam inspection apparatus may further include a compensator and a display unit. The compensator can compensate the initial sensitivity in accordance with the sensitivity difference corresponding to the difference in value between the inspection graph area and the reference graph area. The display unit can display the inspection graph, the reference graph and the experimental graphs.

According to embodiments of the present invention, the operation state of the electron beam inspection apparatus may be readily confirmed by comparing the inspection graph with the reference graph. The sensitivity of the electron beam inspection apparatus may be compensated in accordance with a comparison result between the graphs. Accordingly, there may be no need for repeated performance of the operation state testing process on the electron beam inspection apparatus. Further, in embodiments, the time required for performing the operation state testing process on the electron beam inspection apparatus may be decreased and the throughput of the electron beam inspection apparatus and the productivity of semiconductor devices may be improved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is an example schematic view illustrating an electron beam inspection apparatus, according to embodiments of the present invention.FIG. 2is an example flow chart illustrating a method for testing an operation state of the electron beam inspection apparatus illustrated inFIG. 1. An electron beam inspection apparatus100may include an electron beam source110, a stage140, a driving unit142, a detector144, an image acquisition unit146, an image processing unit148, a graphic unit150, an operation unit152, a compensator154, a memory unit156, and a display unit158.

The electron beam source110may include an electron gun112and a column114. The electron gun112can generate electrons. The column114can form the electrons into an electron beam20and irradiate the electron beam20onto a surface of a substrate10(e.g. a silicon wafer). The electron gun112may include a filament120that emits electrons and an extraction electrode122that extracts electrons. The column114may include an axis adjustment coil124, a magnetic lens130, an aperture126, and/or a scan coil128.

The magnetic lens130may be a cylindrical shaped electromagnet and may collect the electrons by forming an electric field and a magnetic field. The electron beam formed by the electron gun112may have a cross-sectional area of about 10 μm to about 50 μm and a spot size of the electron beam being irradiated onto the substrate10is about 5 nm to about 200 nm. The magnetic lens130may include a pair of condenser lenses132and an objective lens134. The pair of condenser lenses132condenses the electron beam formed by the electron gun112and adjusts the intensity of the electron beam. The objective lens134may adjust the spot size and a focal length of the electron beam being irradiated onto the substrate10.

The axis adjustment coil124may be disposed between the extraction electrode122and the magnetic lens130and may adjust an inclination of an axis of the electron beam formed by the extraction electrode122so that the electron beam is advanced along an optical axis of the magnetic lens130. The aperture126and the scan coil128may be disposed between the condenser lenses132and the objective lens134. The scan coil128may deflect the electron beam transmitted through the aperture126so that the electron beam scans the surface of the substrate10.

The stage140supports the substrate10. The driving unit142is connected to the stage140and adjusts a position of the stage140so that the electron beam20is irradiated onto a predetermined inspection area. The inspection area includes a plurality of scan lines at a predetermined position on the substrate10. A Cartesian robot may be used as the driving unit142. A second driving unit (not shown) for adjusting a height of the stage140may be connected to a lower portion of the stage140. A piezoelectric element may be used as the second driving unit.

The detector144may detect secondary electrons emitted from the scan lines in the inspection area of the substrate10resulting from irradiation from the electron beam20. The detector144may convert a current signal corresponding to the detected secondary electrons into a voltage signal and amplify the voltage signal. A bias voltage for collecting the secondary electrons may be applied to the detector144.

The image acquisition unit146connected to the detector144may convert the amplified voltage signal into image data corresponding to the inspection area of the substrate10. The image data may include gray levels of pixels, each pixel that is part of one of a plurality of inspection images corresponds to scan lines in the inspection area of the substrate10. The image acquisition unit146may serve as an analog digital (AD) converter for converting an analog voltage signal into digital image data.

The image processing unit148connected to the image acquisition unit146may detect defects on the inspection area of the substrate10by analyzing the image data using an initial sensitivity. The image processing unit148may compare the gray levels of the pixels. Each of the pixels that are part of an inspection image are compared with one another to detect the defects on the inspection area. The plurality of scan lines may substantially cover the inspection area and the image processing unit148detects the number of defects corresponding to the scan lines.

The number of defects may be varied in accordance with the initial sensitivity. That is, when the initial sensitivity is set harder (lower) than a predetermined level, a total number of the defects detected on the inspection area may be higher than an actual number of defects. In contrast, when the initial sensitivity is set looser (higher) than the predetermined level, the total number of the defects detected on the inspection area may be lower than the actual number of the defects. Consequently, the total number of detected defects may be inversely proportional to the initial sensitivity.

If an electron beam inspection apparatus is calibrated correctly, the initial sensitivity is substantially identical to a reference sensitivity produced by repeatedly performing the inspection process on a reference substrate. The reference substrate may be manufactured by forming predetermined numbers of defects having predetermined positions.

The graphic unit150connected to the image processing unit148may produce an inspection graph showing the scan lines and the numbers of defects. The operation unit152may compare the inspection graph with a reference graph of the reference substrate using the reference sensitivity. The reference graph may be selected from a plurality of experimental graphs. The experimental graphs may be produced by repeatedly performing the inspection process in a predetermined experimental area on the reference substrate while an experimental sensitivity is gradually increased or decreased.

The detector144may detect secondary electrons emitted from the experimental area of the reference substrate which resulted from irradiation of the electron beam20. Experimental images and an experimental graph are produced from the secondary electrons detected from the experimental area. A plurality of experimental graphs corresponding to a plurality of experimental sensitivities may be produced by repeatedly analyzing the experimental images while the experimental sensitivity is gradually increased or decreased. One of the experimental graphs corresponding to the actual number of defects of the experimental area may be selected for the reference graph. The reference sensitivity is an experimental sensitivity corresponding to the selected reference graph and the experimental graphs may be produced by the image processing unit148and the graphic unit150.

The experimental images, the plurality of experimental graphs, the reference graph and the inspection graph may be stored in the memory unit156, and may be displayed by the display unit158. The operation unit152may compare the inspection graph with the reference graph. The operation unit152may include a first operator for calculating areas of the experimental graphs, a reference graph area and an inspection graph area. The operation unit152may include a comparator for comparing the inspection graph area with the reference graph area and a second operator for determining a sensitivity difference corresponding to a difference in value between the inspection graph area and the reference graph area. Result data that is produced by the operation unit152may be stored in the memory unit156.

The compensator154may compensate the initial sensitivity in accordance with a difference between the inspection graph and the reference graph. The compensator154may compensate the initial sensitivity in accordance with the sensitivity difference corresponding to the difference in value between the inspection graph area and the reference graph area. Alternatively, the sensitivity difference may be produced using an area variation graph showing the area variation of the experimental graphs. The operation unit152may include a third operator for producing the area variation graph showing an area variation of the experimental graphs in accordance with a variable amount of the experimental sensitivity, a functional equation graph showing the area variation, and/or the sensitivity difference corresponding to the difference value between the inspection graph area and the reference graph area. The functional equation may be a simple equation or quadratic equation.

FIG. 3is an example plan view showing a predetermined inspection area on a substrate.FIG. 4is an example enlarged plan view of the inspection area as shown inFIG. 3.FIG. 5is an example enlarged plan view of pixels in the inspection area as shown inFIG. 4.FIG. 6is an example inspection graph indicating the number of defects detected in the inspection area.

A method for testing an operation state of the electron beam inspection apparatus100is shown inFIGS. 1 and 2will be described with reference toFIGS. 1 to 6. In step S100, the substrate10is loaded onto the stage140. The driving unit142adjusts the position of the stage140such that the electron beam20is irradiated onto the predetermined inspection area12of the substrate10supported by the stage140. The inspection area12may be arbitrarily set on the substrate10and includes the predetermined scan lines14substantially covering the entire surface thereof, as shown inFIGS. 3 and 4.

In step S110, the electron beam20scans the inspection area12. The electron beam20generated from the electron beam source110scans the scan lines14sequentially in the inspection area12as shown inFIG. 4. In step S120, the secondary electrons emitted from the inspection area12are detected. The secondary electrons are emitted along the scan lines by means of the irradiation of the electron beam20and are detected by the detector144to which the bias voltage is applied. The detector144converts the current signal corresponding to detected secondary electrons into the voltage signal and amplifies the voltage signal.

In step S130, the inspection images16are then acquired from the secondary electrons. The voltage signal amplified by the detector144is converted into digital image data of the inspection images16corresponding to the scan lines14by the image acquisition unit146.

In step S140, the defects are detected by analyzing the inspection images16. The image processing unit148analyzes the inspection images16using the initial sensitivity, and then detects the defects on the inspection area12by scan lines14. As shown inFIG. 5, a second pixel32has a different gray level from that of a first pixel30adjacent along a first scan line1, and has a substantially identical gray level to that of a third pixel34opposite to the first pixel30. A fifth pixel38has a different gray level from those of a fourth pixel36and a sixth pixel40adjacent along a second scan line2. Here, the second pixel32and the fifth pixel38are detected as the defects. That is, a pixel having a different gray level from at least one of the adjacent pixels or a pixel having a different gray level from all adjacent pixels may be detected as the defects. In the figures, the depicted arrow indicates the scanning direction of the electron beam20.

In step S150, the inspection graph50indicating the number of the defects produced. InFIG. 6, the graphic unit150produces the inspection graph50indicating the number of defects corresponding to the scan lines14. In step S160, the inspection graph50is compared with the reference graph. The inspection graph50and the reference graph are displayed by the display unit158and may be compared by the naked eye.

In step S170, the initial sensitivity used in the inspection process is compensated in accordance with the difference between the inspection graph50and the reference graph. A worker (i.e. a user) may ascertain whether or not the difference between the inspection graph50and the reference graph is within a predetermined tolerance range. When the difference between the inspection graph50and the reference graph exceeds the tolerance range, the initial sensitivity may be adjusted so that the difference is within the tolerance range.

The reference graph may be acquired from the experimental area of the reference substrate and the method for testing the operation state of the electron beam inspection apparatus may also be performed using the reference substrate. In embodiments, the substrate10used in the testing method of the electron beam inspection apparatus is the reference substrate and the inspection area12is the experimental area. In some circumstances, the initial sensitivity may be substantially identical to the reference sensitivity.

When the difference between the inspection graph50and the reference graph exceeds the tolerance range, the operation state of the electron beam inspection apparatus may be judged to be abnormal, which may be due to variations of the electric field and the magnetic field. The variations of the electric field and the magnetic field may be compensated by adjusting the initial sensitivity. Consequently, the operation state of the electron beam inspection apparatus may be restored to a normal state.

FIG. 7is a flow chart illustrating a method of producing a reference graph from an experimental area on a reference substrate andFIG. 8is the reference graph and experimental graphs indicating the number of defects detected in the experimental area of the reference substrate. A method in accordance with example embodiments for acquiring the reference graph will be described with reference toFIGS. 7 and 8.

In step S10, the reference substrate is loaded on the stage140. The driving unit142adjusts the position of the stage140such that the electron beam20is irradiated onto the experimental area of the reference substrate. In step S12, the electron beam20scans the experimental area of the reference substrate. The experimental area includes a plurality of scan lines. The electron beam20transmitted through the column114sequentially scans the scan lines of the experimental area.

In step S14, secondary electrons emitted from the experimental area are detected. The secondary electrons emitted along the scan lines of the experimental area are detected by the detector144to which the bias voltage is applied. The detector144converts the current signal corresponding to detected secondary electrons into the voltage signal and amplifies the voltage signal. In step S16, the experimental images are acquired from the detected secondary electrons. The voltage signal amplified by the detector144are converted into digital image data of the experimental images corresponding to the scan lines of the experimental area by the image acquisition unit146.

In step S18, the defects are detected by analyzing the experimental images. The image processing unit148analyzes the experimental images using the experimental sensitivity and then detects the defects on the experimental area by scan lines of the experimental area.

In step S20, the experimental graph60, which represents the number of defects, is produced. The graphic unit150produces the experimental graph60showing the number of defects corresponding to the scan lines of the experimental area. In step S22, the steps S18and S20are repeatedly performed while the experimental sensitivity is gradually increased or decreased. In step S24, the reference graph70is selected from the produced experimental graphs60. One of the experimental graphs60corresponding to the actual number of the defects on the experimental area may be selected for the reference graph70. The experimental graphs60may be produced by repeatedly performing the steps S10to S20while the experimental sensitivity is gradually increased or decreased.

The display unit158displays the experimental graphs60, the reference graph70, and the inspection graph50. The worker (i.e. a user) may adjust the initial sensitivity in accordance with the sensitivity difference corresponding to the difference between the inspection graph50and the reference graph60. Accordingly, the time required for performing the operation state testing process on the electron beam inspection apparatus may be decreased.

As mentioned above, the method for testing the operation state of the electron beam inspection apparatus may be completed by manually adjusting the initial sensitivity using the inspection graph and the reference graph. However, the method for testing the operation state of the electron beam inspection apparatus may be performed automatically.

FIG. 9is an example flow chart illustrating a method of producing an area variation graph from the experimental area of the reference substrate.FIG. 10is an example flow chart illustrating a method of testing the operation state of the electron beam inspection apparatus using the area variation graph.FIG. 11is an example graph showing an inspection graph area and a reference graph area.FIG. 12is an example graph illustrating one example of a functional equation obtained from the area variation graph.FIG. 13is an example graph illustrating another example of the functional equation obtained from the area variation graph.

InFIG. 9, detailed descriptions of steps S10to S24will be omitted since these steps are similar to those already described in connection with the method for acquiring the reference graph shown inFIG. 7. In step S26, the areas of the experimental graphs60and the reference graph area are calculated. The operation unit152calculates the areas of the experimental graphs60including the reference graph70. The memory unit156stores the areas of the experimental graphs60.

In step S28, the area variation graph80, indicating the area variation of the experimental graphs60, is produced. The operation unit152produces the area variation graph80, indicating the area variation of the experimental graphs60in accordance with a variable amount of the experimental sensitivity. The area variation graph80may be produced from a relationship between the areas of the experimental graphs60and a variable amount of the experimental sensitivity. Further, the area variation graph80may be produced from a relationship between a variable amount of the area of the experimental graph60and the variable amount of the experimental sensitivity.

In step S30, the functional equation is produced from the area variation graph80. The functional equation is produced by the operation unit152and may be a simple equation 90b or a quadratic equation 90a.

InFIG. 10, steps S200to S250are similar to those already described in connection with the method for testing the operation state of the electron beam inspection apparatus shown inFIG. 2, thus detailed descriptions of the steps S200to S250are omitted. In step S260, inspection graph area (A) is calculated. Alternatively, the inspection graph area (A) may be calculated by the operation unit152.

In step S270, the inspection graph area (A) and reference graph area (B) are compared to each other using the area variation graph80. The operation unit152compares the inspection graph area (A) with the reference graph area (B) using the area variation graph and calculates the sensitivity difference corresponding to the difference in value between the inspection graph area (A) and the reference graph area (B).

In step S280, the initial sensitivity is compensated in accordance with the sensitivity difference corresponding to the difference in value between the inspection graph area (A) and the reference graph area (B). The compensator154adjusts the initial sensitivity in accordance with the sensitivity difference to restore the electron beam inspection apparatus100to a normal operation state.

In embodiments, the operation unit152may produce a different value that is between the inspection graph area (A) and the reference graph area (B) using the functional equation graph80, representing the area variation.

Table 1 shows the area variation of the experimental graphs in accordance with the variable amount of the experimental sensitivity.

Referring to Table 1 andFIG. 12, the area variation graph80may be expressed with the quadratic equation (90a) as follows:
y=3×106x2−842.86x+115.05  (90a)

where, y is the area of the experimental graph60, and x is the variable amount of experimental sensitivity.

For example, when the reference graph area (B) is 110.5, and the inspection graph area (A) is 400, the sensitivity difference is approximately 0.01. Here, the operation unit152calculates the sensitivity difference using the quadratic equation (90a), and the compensator154adjusts the initial sensitivity in accordance with the calculated sensitivity difference. That is, the compensator154adjusts the initial sensitivity to be loose by about 0.01.

Referring toFIG. 13, the area variation graph80may be also expressed with the simple equation (e.g. a linear equation) (90b) as follows:
y=42343x−68.441  (90b)

where, y is the variable amount of the experimental graph area, and x is the variable amount of experimental sensitivity.

As mentioned above, though performed using the area variation graph and the functional equation (90a or 90b) produced from the reference substrate, the method for testing the operation state of the electron beam inspection apparatus may be performed using an area variation graph and a functional equation produced from a substrate on which various patterns or layers are formed.

According to embodiments of the present invention, the initial sensitivity may be compensated in accordance with the sensitivity difference corresponding to the difference in value between the inspection graph area and the reference graph area. The sensitivity difference may be readily calculated by means of the area variation graph or the functional equation.

Accordingly, there may be no need to repeatedly perform the operation state testing process of the electron beam inspection apparatus in order to adjust the electric field and the magnetic field of the magnetic lens, thereby decreasing the time required for the operation state testing process. Further, throughput of the electron beam inspection apparatus may be increased.

In the drawings and specification of the present invention, there have been disclosed embodiments of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.