JPH0445083B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pattern length measurement method using charged particle beam scanning.

[Prior Art] In recent years, integration has progressed from ICs to LSIs and super LSIs, and patterns have become smaller along with this. Due to the miniaturization of patterns, methods that use electron beams, which have higher resolution than those that use light, are attracting attention as methods for measuring the width of patterns.

In this method of using an electron beam, the pattern to be measured is brought to the high-magnification scanning area of the electron beam, the electron beam is scanned over the pattern, and the length is measured based on the reflected electrons and secondary electron detection signals. This is the way to do it.

By the way, when a pattern to be measured is brought into the high-magnification scanning area of the electron beam, the mark is usually scanned near the position of a mark that has been placed in advance at an appropriate position on the material on which the pattern has been drawn. The position is detected, and from this position, the stage on which this material is placed is moved based on the position of the pattern with respect to the mark position known in advance, and the center of the pattern to be measured is brought to the scanning center of the electron beam. It's coming too. However, because the pattern may be formed on the material at a position slightly shifted from a predetermined position, the center of the pattern may not necessarily be located in the high-magnification scanning area (the center of the low-magnification scanning area).

[Problem to be solved by the invention] In such a case, while observing a low-magnification pattern image on a cathode ray tube screen, the stage is manually moved so that the center of this pattern is at the center of the screen. ing.

However, such operations take time.

The present invention is aimed at solving such problems.

[Means for Solving the Problems] Therefore, the pattern length measurement method of the present invention scans the pattern with a charged particle beam, and determines the pattern length based on reflected electrons or secondary electron detection signals generated from the pattern by this scanning. In a pattern measurement method in which the coordinates corresponding to multiple edges of the pattern are determined and the pattern width dimension is calculated based on these coordinates, a lower magnification than when measuring the pattern width dimension is used before pattern width measurement. scan the pattern to be measured, determine the coordinates of the plurality of edges of the pattern based on the detection signals obtained by this scanning, detect the center position of the pattern based on the coordinates, and determine the center position of the pattern. A calculation system calculates the deviation between the scanning center position of the charged particle beam and the scanning center position of the charged particle beam, and the calculation system sends a command to the stage movement mechanism to move the stage by an amount corresponding to this deviation, thereby moving the material in which the pattern has been created. Either the stage on which it was placed was moved, or the scanning start position of the charged particle beam was shifted by an amount corresponding to this shift when measuring the pattern width dimension.

[Example] FIG. 1 shows an example of an apparatus implementing the pattern length measurement method of the present invention. In the figure, 1 is an electron gun, and an electron beam emitted from this electron gun is focused by a focusing lens 2 onto a material 3 on which a pattern has been drawn in a previous step. Further, this electron beam is transmitted to a scanning signal generating circuit 5 operated by a command from a control device 4.
The material 3 is scanned by the deflector 6, which operates according to a scanning signal from the deflector 6. The reflected electrons generated on the material 3 by this scanning are detected by the reflected electron detector 7. The output of this detector is sent to the control device 4 via the amplifier 8, and at the same time, an output (scanning signal) synchronized with the output from the scanning signal generating circuit 5 to the deflector 6 is supplied. It is also sent to the cathode ray tube 9. This cathode ray tube is
Due to the brightness modulation, one marker M can be placed at a position on the screen according to a command from the control device 4. Incidentally, the position of this marker M can also be controlled by external operation. Reference numeral 10 denotes a stage on which the material is placed, and is moved by a command from a stage moving mechanism 11 which is activated by a command from the control device 4.

Now, for example, the pattern shown in Figure 2 a
The case of measuring the width dimension of _P1 in the X direction will be described below.

First, a low magnification (for example, 5000
), the electron beam passes through the pattern P ₁ on material 3.
A predetermined position is scanned in the X direction. The backscattered electrons generated from the pattern P ₁ by this scanning are detected by the backscattered electron detector 7 and sent to the control device 4 via the amplifier 8 . This control device inverts the negative level signal portion (Fig. 2 c) of the signal based on such reflected electrons (Fig. 2 b), and
Time values ta, tb, tc, and td are detected from a certain scanning time t ₀ of the signal shown in FIG. These time values are determined by the number of clock pulses generated from time _t0 to times a, b, c, and d. These detected values
From ta, tb, tc, and td, calculate (ta+td)/2 to find the center position x _c of this pattern in the X direction. If the number of clock pulses to this center position is, for example, 100, the total amplitude when the electron beam is swung on the pattern at the low magnification (5000 times) is 20 μm, and the number of clock pulses corresponding to this total amplitude is 1000, then , the control device 4 determines that the center _C1 of this pattern in the X direction is equal to the number of clock pulses 500 by the following calculation.
Calculate that the center of the cathode ray tube screen corresponding to _C10 is shifted to the left by 20 x (500 - 100) / 1000 = 8 μm.

Therefore, the control device 4 controls the stage moving mechanism 11.
Then, a command is sent to move the stage 10 by 8 μm to the right in the X direction. This command causes the stage 10 to move 8 μm to the right in the X direction, so that the center C ₁ of the pattern P ₁ coincides with the center C ₁₀ of the screen.

Next, as shown in FIG. 3a, the electron beam is directed to the pattern P ₁ on the material 3 at a high magnification (for example, 50,000 times) by a signal from the scanning signal generation circuit 5 that receives a command from the control device 4. ' is scanned in the X direction. The reflected electrons generated from the pattern P ₁ ' by this scanning are detected by the reflected electron detector 7 and sent to the control device 4 via the amplifier 8. This control device inverts the negative level signal portion (Fig. 3 c) of the signal based on such reflected electrons (Fig. 3 b), so that the signal shown in Fig. 3 c) is Temporal values ta′, tb′, tc′ from the scanning time t ₀ ′ to the time points a′, b′, c′, d′ when the preset level Le is reached
，
Detect td′. These time values are determined by the number of clock pulses generated from time t ₀ ' to time a', b', c', and d'. These detected values ta′, tb′,
From tc' and td', calculate (td'-ta'), and use this as the width dimension of pattern _P1 .

If it is necessary to measure the width dimensions in the X and Y directions of a grid pattern as shown in Figure 4, the positional deviation in the Y direction can also be calculated at low magnification in the same way as above. , calculate the deviation of the center position _C0 of the pattern in the X and Y directions with respect to the center position of the screen in the X and Y directions, move the stage in the X and Y directions by the amount corresponding to these positional deviations, and measure. Move the center of the pattern to the center of the screen and measure the width of the pattern at high magnification.

Further, in the above embodiment, the center position of the pattern is made to coincide with the center of the screen by moving the stage by an amount corresponding to the deviation between the center position of the pattern and the center position of the screen. Instead, when measuring the pattern width dimension, shift the scanning start position of the charged particle beam in the direction opposite to the direction in which the deviation occurs by an amount corresponding to the deviation between the center position of the pattern and the center position of the screen. Even if you start scanning,
The pattern width dimension can be measured in a display state in which the center of the pattern coincides with the center of the screen. In the latter measurement, unlike the former measurement, the mechanical movement of the stage is not involved, but it is performed using electrical movement.
The latter measurement method has fewer errors and is faster than the former measurement method.

[Effect of the invention] When the center of the pattern is located at the scanning center of the charged particle beam, there is no need to manually move the stage so that the pattern to be measured is at the center of the screen, as in the past. Since this is done automatically, the operation does not take much time and does not place any burden on the operator.

[Brief explanation of drawings]

Figure 1 shows an example of an apparatus implementing the pattern length measurement method of the present invention, Figures 2 and 3 are for supplementary explanation of the operation of the present invention, and Figure 4 shows another example of a pattern. This is what is shown. 1: Electron gun, 2: Focusing lens, 3: Material, 4:
Control device, 5: Scanning signal generation circuit, 6: Deflector,
7: backscattered electron detector, 8: amplifier, 9: cathode ray tube, 10: stage, 11: stage moving mechanism.

Claims (1)

[Claims] 1 Scan the pattern with a charged particle beam, determine the coordinates corresponding to multiple edges of the pattern based on the reflected electrons or secondary electron detection signals generated from the pattern by this scanning, and calculate the width of the pattern based on these coordinates. In the pattern length measurement method that calculates the dimension, before measuring the pattern width dimension, the pattern to be measured is scanned at a lower magnification than when measuring the pattern width dimension, and based on the detection signal obtained by this scanning. The coordinates of the plurality of ends of the pattern are determined using the coordinates, the center position of this pattern is detected based on the coordinates, the deviation between this center position and the scanning center position of the charged particle beam is calculated by a calculation system, and the calculation system Then, by sending a command to the stage moving mechanism to move the stage by an amount corresponding to this deviation, the stage on which the material on which the pattern has been created is placed can be moved, or alternatively, the pattern width dimension can be changed by an amount corresponding to this deviation. A pattern length measurement method that shifts the scanning start position of a charged particle beam during measurement.