JPH03262908A - Electron beam coordinate measuring instrument - Google Patents

Abstract

PURPOSE:To accurately correct a deflection gain according to the correction value for deflection width by moving one sample through an XY stage by an optional distance in the deflection range of an electron beam and calculating the accurate correcting value for the deflection width from its movement quantity and a value measured with the electron beam. CONSTITUTION:The electron beam 3 which is led out of an electron gun 1 is converged by electron lenses 2a and 2b to irradiate the sample 8. Further, the electron beam 3 is deflected by optional width through a deflecting coil 4. A secondary electron which is discharged when the sample 8 is irradiated with the electron beam 3 can be detected by a secondary electron detector 5. The sample 8 is fixed on the stage 6, which is driven in an X and a Y direction by a motor 11; and it position is measured by a laser length measurement system 7. Further, a stage control system 10 accurately positions the stage 6 according to the measured value of the system 7. A sample image, on the other hand, is projected on a cathode-ray tube 9 with the secondary electron signal which is detected 5 and a deflecting signal sent to the coil 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron beam coordinate measuring device that measures the position of a circuit pattern formed on a Si wafer, a glass mask, or the like using an electron beam.

[Conventional technology]

In conventional equipment, the electron beam deflector (magnification) is calibrated by measuring a sample whose dimensions are already known, and then manually adjusting the gain of the deflector amplifier based on the measurement results.

-Alternatively, a sample whose dimensions were already known was measured and errors were corrected using software.

[Problem to be solved by the invention]

The above-mentioned conventional technology requires a sample (reference sample) whose dimensions are already known, and the dimensions must also be accurate. The problem is how to measure the dimensions of the standard sample and what kind of measuring device to use. After all, the dimensions of the reference sample naturally include some error. In other words, with conventional technology, it is not possible to achieve higher accuracy than with a measuring machine that measures the dimensions of a reference sample, and depending on the magnification,
The size of the sample must also be changed, and many reference samples must be prepared.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a highly accurate electron beam coordinate measuring device that can perform accurate and simple deflector calibration.

[Means to solve the problem]

In order to achieve the above purpose, X
Using a measuring instrument that measures the position of the Y stage, such as a laser interferometer, one sample (pattern) is moved on the XY stage by an arbitrary distance within the deflection range of the electron beam.
An accurate correction value for the deflector is calculated by calculating the amount of movement and a value measured with an electron beam, and based on this, accurate deflection gain correction is performed.

[Effect]

Since the deflection gain correction described above uses a laser interferometer as a source, an accurate correction value can be obtained and accurate correction can be performed. This allows the exact coordinates of the sample to be determined.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, and 4.

The outline of the apparatus and measurement principle of the present invention will be explained with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram of the apparatus, and an electron beam 3 extracted from an electron gun 1 is focused by electron lenses 2a and 2b and irradiated onto a sample 8. Further, the electron beam 3 is deflected by an arbitrary width by a deflection coil 4.

Secondary electrons emitted when the sample 8 is irradiated with electrons 1!3 can be detected by the secondary electron detector 5. Here, the sample 8 is fixed to a stage 6, the stage 6 is driven in the XY force directions by a motor 11, and its position can be accurately measured by a laser length measurement system 7. The stage control system 10 performs accurate positioning of the stage 6 based on the measured values of the laser length measurement system 7, and also uses the secondary electron signal detected by the secondary electron detector 5 and the deflection sent to the deflection coil 4. A sample image is projected onto the cathode ray tube 9 based on the signal.

Next, the principle of sample measurement using the above device will be explained with reference to FIG. - As an example, if we consider measuring the position of a pattern 12 with a width of several μm etched on a Si substrate, first, the sample is moved to a designed position 15 of the pattern 12. Here, if the stop position of the stage is 14, a stop error Le occurs, and the electron beam 3 is corrected by the error by the deflection coil 4 so that the deflection center for measurement coincides with the design position 15 of the pattern 12. Make it.

At the cathode ray tube association, the deflection center (designed position 15) is the center of the screen, and the electron beam 3 is scanned 13 by the deflector 4.
Then, the pattern edge is determined from the secondary electron signal, and its center is measured as the deviation amount Lb of the pattern 12 from the designed position 15. Therefore, the coordinates of the pattern 12 are Ls+Le+Lb, where Ls is the stop coordinate of the stage. Here, the measurement accuracy of Le and L is that scan 13 is
Determined by how accurately it is deflected.

The deflection output calibration of the scan 13 will be described below with reference to FIGS. 3 and 4. First, the correction function for the stage stop error Le explained above is deleted so that no correction is applied. In this state, move the stage so that the pattern 12 can be seen at the right edge of the screen of the cathode ray tube. Here, measure the distance Lbz from the center of the pattern 12. First, move the stage by ΔLs and measure the distance from the center of the pattern 12. Measure Lbx. In the above measurement, the amount of movement ΔLs of the stage and the amount of deviation 16 of the pattern 12 on the screen
1+Lbz must match, if they do not match, the deflector is inaccurate and the deflector is corrected.
As shown in the figure, ΔLs is measured by a laser length measurement system, Lbx and Lb2 are determined from the secondary electron signal, and each is sent to the CPV 18 and a correction value ε is determined from t = (Lbr+Lbz−ΔLS)yΔLs. With this correction value ε, the deflection device is set to L=Ld Xε and is sent to the deflection coil 4 as a correct deflection device.

Of course, this ε is also used to correct the stop error Le of the stage.
Corrections are included.

According to this embodiment, the amount of deflection of the electron beam by the deflector can be matched with the laser length measurement system that measures the coordinates of the stage, so the coordinates of the pattern can be accurately measured. Also, since it is possible to calibrate during deflection with one pattern,
There is no need to change the calibration pattern depending on the magnitude of deflection, that is, the magnitude of magnification. Furthermore, since the center position of the calibration pattern is detected, there is no need to create a special pattern with high dimensional accuracy.

〔Effect of the invention〕

According to the present invention, since the deflection of the electron beam can be corrected in an accurate and simple manner, it is effective in accurately measuring the position of the sample.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the present invention, FIG. 2 is a diagram of the principle of measurement, FIG. 3 is a diagram of the principle of calibration, and FIG. 4 is a schematic diagram of the apparatus using the present invention. 3... Electron beam, 4... Deflection coil, 5... Secondary type, child detector, 6... Stage, 7... Laser length measurement system, 2 C′ξ-shi\-I / Figure 1 Figure 2

Claims (1)

[Claims] 1. An electron source that generates an electron beam, an electron lens for converging the electron beam, a deflector for deflecting the electron beam, an XY stage for moving the sample to be measured within the XY plane, and the A measuring device that can accurately measure the position of the XY stage, a detector that collects reflected electrons or secondary electrons obtained when the electron beam scans the sample to be measured, and a control system that controls them. An electron beam coordinate measuring apparatus characterized in that the electron beam coordinate measuring apparatus further comprises means for calibrating the deflection length of the electron beam by the deflector and a measuring device for measuring the position of the XY stage.