Method for correcting image drift of transmission electron microscope in real time and control module

Abstract

The invention provides a method for correcting image drift of a transmission electron microscope in real time. The method comprises the following steps: providing a sample holder which is used for fixing a sample to be detected; setting a calibration point on the sample rack; environment variables are changed, and the drift distance of the calibration point is recorded; executing the steps for multiple times to form a curve of the environment variable and the drift distance; and applying the curve to the tracking operation of the sample to be tested after temperature change. According to the technical scheme, the curve is formed and is used for tracking the sample in the determined direction and distance according to the guidance of the curve after the environment variable is changed, so that test result omission caused by the condition that the sample drifts out of the view range due to the change of the environment variable is avoided as far as possible, the test time is saved, and the experiment efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of testing technology, and in particular to a method for real-time correction of transmission electron microscope image drift and a control module. Background Art

[0002] Observing the microstructure of samples using a transmission electron microscope is currently the most direct means of observing microelectronic components. The existing observation method usually uses FIB sample preparation to obtain slices of the required component structure and places them on a transmission electron microscope sample holder for observation. During the observation process, external loads such as temperature field, electric field, and magnetic field can also be applied to the sample to further observe the structural characteristics of the component.

[0003] However, in the case of the above-mentioned additional environmental variables, the drift distance will be too large, causing the observation area to be out of the field of view, and the image will become blurred if the sample focus difference is too large. The above two situations cannot be solved by software image processing. Because the field of view range is only 50nm×50nm at high magnification, assuming that the lateral displacement is <25nm and the longitudinal focus difference is less than 200nm, the image is still clear and traceable, but once it exceeds this range, it cannot be tracked, which brings great difficulties to observation. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for real-time correction of transmission electron microscope image drift, which can quickly track samples when environmental variables change.

[0005] In order to solve the above problems, the present invention provides a method for real-time correction of transmission electron microscope image drift, comprising the following steps: fixing a sample to be tested on a sample holder for TEM observation; setting a calibration point on the sample holder; changing environmental variables and recording the drift distance of the calibration point; performing the above steps multiple times to form a curve of environmental variables and drift distances; and using the curve for tracking operations after the sample to be tested changes temperature.

[0006] Optionally, the environmental variable is selected from one of temperature, humidity, magnetic field and electric field.

[0007] Optionally, the sample holder is replaced and the above steps are repeated to form another environmental variable versus drift distance curve.

[0008] Optionally, the drift distance includes drift distances in three directions of X, Y, and Z, and three curves are formed accordingly.

[0009] Optionally, the changing of the environmental variables includes at least one of increasing the environmental variables from room temperature to a target environmental variable and decreasing the environmental variables from the target environmental variable to room temperature.

[0010] Optionally, setting a calibration point on the sample rack includes providing a standard sample with the calibration point and fixing it on the sample rack.

[0011] Optionally, the sample rack includes a tray, the tray has a through hole at the center, and the sample is placed in the through hole. The number of the through holes is multiple.

[0012] Optionally, the sample to be tested includes any one of a diode, a triode, a transistor, an inductor, and a capacitor, or an integrated circuit composed of multiple types.

[0013] In order to solve the above problems, the present invention provides a control module, including an environmental variable control module and a sample stage control module, and the control module is configured to perform the following steps: fix the sample to be tested on a sample rack for TEM observation; set a calibration point on the sample rack; change the environmental variables and record the drift distance of the calibration point; perform the above steps multiple times to form a curve of environmental variables and drift distances; and use the curve for sample tracking operations after the environmental variables are changed.

[0014] The above technical solution forms a curve for tracking samples in a certain direction and distance according to the guidance of the curve after the environmental variables change, thereby avoiding to the greatest extent the omission of test results caused by the sample drifting out of the field of view due to the change of environmental variables, saving test time and improving experimental efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Attached Figure 1 Shown is a schematic diagram of the implementation steps of a method for real-time correction of transmission electron microscope image drift provided by a specific embodiment of the present invention.

[0016] Attached Figure 2 Shown is a schematic structural diagram of a sample rack used in a specific embodiment of the present invention.

[0017] Attached Figure 3 The attached Figure 2 Schematic diagram of the enlarged structure of the sample placement area indicated by the arrow.

[0018] Attached Figure 4 The attached Figure 3 A further enlarged schematic diagram of the through hole where the sample is located.

[0019] Attached Figure 5 Shown are three curves corresponding to the drift distances in the X, Y and Z directions obtained by the method described in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following is a detailed description of the method for real-time correction of transmission electron microscope image drift and the specific implementation of the control module provided by the present invention in conjunction with the accompanying drawings.

[0021] A specific embodiment of the present invention provides a method for real-time correction of transmission electron microscope image drift, comprising the following steps: fixing the sample to be tested on a sample holder for TEM observation; setting a calibration point on the sample holder; changing the environmental variable and recording the drift distance of the calibration point; performing the above steps multiple times to form a curve of environmental variable and drift distance; using the curve for tracking operation after the sample to be tested changes temperature. The environmental variable is selected from one of temperature, humidity, magnetic field, and electric field. Due to the complex structure of the sample holder, it is difficult to accurately estimate the direction and distance of sample drift when the environmental variable changes by calculation, and it is necessary to search for the sample again in all directions, which brings great trouble to the observation. Taking temperature change as an example, a specific implementation method of how to solve the above problem is given below. Under the influence of other variables such as humidity, magnetic field, and electric field, if the sample drifts, the following method can also be used to implement tracking.

[0022] Attached Figure 1 The figure shows a schematic diagram of the implementation steps of a method for real-time correction of transmission electron microscope image drift provided by a specific embodiment of the present invention. Taking temperature as an environmental variable, the method comprises: step S10, fixing the sample to be tested on a sample holder for TEM observation; step S11, setting a calibration point on the sample holder; step S12, changing the temperature and recording the drift distance of the calibration point; step S13, performing the above steps multiple times to form a curve of temperature and drift distance; step S14, using the curve for tracking operation after the sample to be tested changes temperature.

[0023] Referring to step S10, the sample to be tested is fixed on a sample holder for TEM observation. Figure 2 FIG. 1 is a schematic diagram of a specific implementation of the sample rack used in this step. Figure 3 The diagram shows an enlarged schematic diagram of the area for placing samples indicated by arrows. In this specific embodiment, the sample holder 10 includes a tray 11, and the center of the tray 11 has a through hole 12, and the sample to be tested is placed in the through hole 12. The edge of the sample to be tested is fixed to the edge of the through hole 12 according to its morphology. The number of the through holes 12 can be one or more, and in this specific embodiment, it is multiple, and the inner diameter is the same, which is 10 μm.

[0024] Referring to step S11, a calibration point is set on the sample rack 10. The set calibration point can be any point within the range of the through hole 12 of the tray 11, and as shown in the attached Figure 4The figure shows a further enlarged schematic diagram of the through hole 12. Preferably, a standard sample 13 with a calibration point 131 is used and fixed in the tray 11 of the sample holder 10.

[0025] Referring to step S12, the temperature is changed, and the drift distance of the calibration point 131 is recorded, and step S13 is performed multiple times to form a curve of temperature and drift distance. In this specific embodiment, the specific way to change the temperature is to increase the temperature of the test environment from room temperature to 800°C, and record the drift distance of the calibration point 131 once every 50°C, and the drift distance includes the drift distances in the three directions of X, Y, and Z, and three curves are formed accordingly. Since the field of view range under high magnification is only 50nm×50nm, when the drift distance in the X and Y directions is <25nm, it can be directly measured. When the drift distance in the X and Y directions exceeds 25nm, the drift distance can be determined by combining a reference object with an enlarged scale. When the longitudinal gap of the focus, that is, the Z direction is less than 200nm, the image is still clear and traceable. When it exceeds this range, the focus can be adjusted up and down to be clear, and the drift in the Z direction can be calculated by the change of the focal length. The above method requires repeated execution and calculation to obtain more accurate results, but the purpose of this method is to establish a standard curve to guide subsequent measurements, so from the perspective of the overall test process, it can save test time. Figure 5 Shown are three curves corresponding to the drift distances in the three directions of X, Y and Z obtained by the above method.

[0026] Referring to step S14, the curve is used for tracking operations after the temperature of the sample to be tested changes. The sample to be tested includes any one of a diode, a triode, a transistor, an inductor, a capacitor, or an integrated circuit composed of multiple types. After the above-mentioned electronic components or integrated circuits are sliced ​​and fixed by FIB, the transmission electron microscope observation process will focus on several key points of interest, such as the gate dielectric layer of MOSFET, the dielectric layer between the electrode plates of the capacitor, etc. And it is necessary to observe the changes in these structures when the temperature changes. However, the deformation of the sample holder caused by temperature changes will cause these points of interest to drift out of the field of view. Attached Figure 3 In the curve shown, the data within the gray range is the data that can be captured without adjusting the lens parameters within the field of view. Beyond this range, it is necessary to adjust the lens position and parameters to capture. If there is no such curve, then in each test process, once the point of interest that needs to be observed on the sample drifts out of the field of view, it is necessary to move the lens in all directions to capture the point, which takes a lot of testing time. By using the above curve, you can search in the direction and data range specified by the curve. Even if the point of interest cannot be accurately captured in the center of the field of view, because the field of view itself has a range of 50nm×50nm and a focus margin of 200nm, the above curve is sufficient to make the point of interest appear quickly within the field of view.

[0027] In another specific embodiment, when the sample holder provided in step S10 is changed, considering that different sample holders have the same or similar structures, the influence of material uniformity and processing accuracy may also cause the deformation to be different when the temperature changes. Therefore, a preferred embodiment is to re-execute the above steps to form a new set of test curves, and record the mapping relationship between the curves and the sample holders.

[0028] In another specific embodiment, the specific method of changing the temperature in step S12 can be to lower the temperature of the test environment from 800°C to room temperature, and record the drift distance of the calibration point every 50°C. Since hysteresis may exist for some materials during the heating and cooling process, the heating and cooling may not execute the same curve. Therefore, a preferred embodiment is to measure two different curves in the heating and cooling stages to guide subsequent sample testing. The drift distance can also be described in polar coordinates, recording the drift amounts of angle and distance respectively, and forming a corresponding mapping relationship.

[0029] A specific embodiment of the present invention is given above by taking temperature as an example. It should be noted that the environmental variable is selected from one of temperature, humidity, magnetic field, and electric field. Under the influence of other variables such as humidity, magnetic field, and electric field, if the sample drifts, the following method can also be used to implement tracking. Therefore, the above environmental variables should also be regarded as the reasonable overview and protection scope of the present invention.

[0030] As a specific implementation of a control module, the control module includes a temperature environment variable control module and a sample stage control module, and the fixing of the sample to be tested on a sample rack for TEM observation is configured to perform the following steps: providing a sample rack, the sample rack is used to fix the sample to be tested; setting a calibration point on the sample rack; changing the environmental variable and recording the drift distance of the calibration point; performing the above steps multiple times to form a curve of environmental variable and drift distance; using the curve for sample tracking operation after the environmental variable is changed. The environmental variable control module is used to control the environmental variables of the test environment, and the lens control module is used to observe the sample and record the drift distance to form a test curve. The environmental variable is selected from one of temperature, humidity, magnetic field, and electric field.

[0031] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for real-time correction of transmission electron microscope image drift, characterized in that: The method comprises the following steps: fixing the sample to be tested on a sample holder for TEM observation; setting a calibration point on the sample holder; changing the environmental variables and recording the drift distance of the calibration point; performing the above steps multiple times to form a curve of the environmental variables and the drift distance; and using the curve for sample tracking operation after the environmental variables are changed.

2. The method according to claim 1, characterized in that The environmental variable is selected from one of temperature, humidity, magnetic field and electric field.

3. The method according to claim 1, characterized in that The sample holder is replaced and the above steps are repeated to generate additional environmental variable versus drift distance curves.

4. The method according to claim 1, characterized in that: The drift distance includes drift distances in three directions, namely, X, Y, and Z, and three corresponding curves are formed.

5. The method according to claim 1, characterized in that The changing of the environmental variables includes at least one of increasing and decreasing the environmental variables to room temperature.

6. The method according to claim 1, characterized in that The step of setting a calibration point on the sample rack comprises providing a standard sample with the calibration point and fixing the standard sample on the sample rack.

7. The method according to claim 1, characterized in that The sample rack to be tested comprises a tray, the center of the tray is provided with a through hole, and the sample to be tested is placed in the through hole.

8. The method according to claim 7, characterized in that The number of the through holes is multiple.

9. The method according to claim 1, characterized in that: The sample to be tested includes any one of a diode, a triode, a transistor, an inductor, and a capacitor, or an integrated circuit composed of multiple types.

10. A control module, comprising an environmental variable control module and a sample stage control module, characterized in that: The control module is configured to perform the following steps: fix the sample to be tested on a sample holder for TEM observation; set a calibration point on the sample holder; change the environmental variables and record the drift distance of the calibration point; perform the above steps multiple times to form a curve of environmental variables and drift distances; and use the curve for sample tracking operations after the environmental variables are changed.

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