JPH0658221B2 - Scanning electron microscope - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a scanning electron microscope, and is particularly suitable for automatically measuring the dimensions of a fine pattern width, a pitch, etc. on a wafer displayed on an image display unit. The present invention relates to a scanning electron microscope equipped with various means.

BACKGROUND OF THE INVENTION In conventional scanning electron microscopes used for dimension measurement of wafers and the like, as described in Japanese Utility Model Laid-Open No. 61-24606, the edge roughness of a signal and a pattern having a good S / N ratio. When measuring the dimension using the signal obtained by averaging, the signals around the specified position were averaged. The averaging means adding and averaging the signals above and below in the dimension measuring direction and the vertical direction.

However, it did not show the range of the area to be averaged. Therefore, in order to confirm what range the area is, the operator has employed a method of calculating a specified area and checking the object difference by applying it to the screen. As a result, it puts an extra burden on the operator,
There was a problem in terms of throughput.

FIG. 5 is a diagram showing an example of CRT display in the conventional automatic length measurement.

In the conventional automatic length measurement, an instruction is sent from the electronic computer to the cursor generator, and first, as shown in FIG. 5 (a), the pattern 21 and the cursor 22 are displayed on the CRT. The cursor 22 can be moved to the length measurement position by controlling the movement by an external operation (for example, operation of a track ball), and can be displayed by overlaying it on the CRT using an adder.

Next, as shown in FIG. 5 (b), the cursor 22 which is the designated length measurement position in FIG. 5 (a) is set as a center and is set in advance in the i direction which is the direction perpendicular to the length measurement dimension direction. The addition and averaging is performed based on the number of additions n and the interval s between the lines. That is, if values are added at intervals s in the i direction and the current number of additions is n, the value of the m pixel is
Addition value up to (n-1) [However, A (i, m) is a value in the i direction of the mth pixel]
And the nth A (n, m) are added and averaged. This process is performed for the planeme at the designated position for length measurement, and the signal thus obtained is used to perform automatic length measurement processing using an electronic computer. However, as an implementation method, although the arithmetic mean of the signals once captured in the image memory is described here, there is no problem even if this is implemented by a hardware method.

As a result, as shown in FIG. 5 (c), the cursors 23, 24, 25 are respectively placed at the length measuring position and the edge determining position.
Is displayed, and the measured value is automatically calculated by the electronic computer based on the interval 1 between the cursors 24 and 25.

As described above, since only the cursor 22 at the length measurement position is displayed, the area to be averaged or the averaged area is not clear. Therefore, as described above, a work of calculating which area the operator is averaging and confirming it with a finger or the like is involved, which imposes an extra burden on the operator.

[Object of the Invention]

The present invention has been made in view of the above, its object is to be able to automatically measure the fine pattern width on the wafer displayed in the image display unit, the dimensions of the pitch, etc. An object of the present invention is to provide a scanning electron microscope that allows an operator to easily confirm the area to be scanned or the averaged area.

[Outline of Invention]

A feature of the present invention is to provide a length measuring means for automatically performing length measurement using a signal having a good S / N ratio obtained by averaging the signals in the vertical direction and the dimension in the dimension measurement direction around the designated position. , And a display means for displaying the area to be averaged.

Example of Invention

Hereinafter, the embodiment of the present invention shown in FIG. 1 and FIGS.
This will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the scanning electron microscope of the present invention. In FIG. 1, an electron beam 2 emitted from an electron source 1 is finely converged by a converging lens 3 and an objective lens 5 and focused on a sample 6. Further, the electron beam 2 is a deflection coil 4 which operates according to a signal from the deflection generator 9 according to a control command from the electronic computer 13.
Then, the sample 6 is scanned in a two-dimensional manner, and the sample 6 is scanned. At this time, the signals of the secondary electrons 7 and the like generated from the sample 6 are detected by the detector 8 and are A / D converted and then stored in the image memory 10. At the same time, the signals are also D / A converted to the CRT.
An image is displayed on 14 as a brightness modulation signal. By the way, in the present invention, as shown in FIG. 2A showing the CRT display in the automatic length measurement by the scanning electron microscope, the addresses of the upper end and the lower end of the area to be averaged are the addition number n and the interval s. It is possible to calculate the upper end address = P− (n * s) / 2 …… (1) and the lower end address = P + (n * s) / 2 …… (2) by using the measurement center position P. The cursors 16 and 17 are displayed by the cursor generator 12 at positions corresponding to. In addition, 11 is an adder.

These cursors 16 and 17 are connected to the track ball 15 as an external operation, and as an example, the number of pulses generated by moving the track ball 15 is counted. The width (m * s; n is the number of additions, and s is the interval) is moved. After the automatic length measurement, as shown in FIG. 2 (b), cursors 18 and 19 indicating the averaged areas are displayed on the CRT 14.

In addition, in the area to be averaged, the number of additions and the interval can be set in advance by the operator.
The width of the area displayed at T14 can also be changed.

According to the embodiment of the present invention described above, it is possible to easily confirm the area to be averaged or the averaged area.

By the way, when it is desired to measure the average size of the entire pattern, the area to be averaged is set between the cursors 20 and 21 as shown in (a) of FIG. 3 which is an explanatory view of an application example of the present invention. When the number of additions and the interval are set so as to be wide, and the local dimension is to be measured, as shown in FIG. 3B, the area to be averaged is narrowed between the cursors 20 and 21. It suffices to set the number of additions and the interval. Therefore, the operator can easily perform work while checking on the CRT 14 when changing the area to be averaged according to the use, and the burden on the operator can be reduced.

Further, in the case of a shape as shown in FIG. 4 (a) which is an explanatory view of another application example of the present invention, when the area to be averaged is wide as shown in FIG. 4 (a), Since an appropriate measurement value cannot be obtained, as shown in Fig. 4 (b),
It is necessary to reset to an appropriate area for averaging, but it can be said that this is also an effective display method in such cases.

However, the number and types of cursors (eg, points, solid lines, etc.) need not be limited to those shown in the embodiments.

〔The invention's effect〕

As described above, according to the present invention, it is possible to automatically measure the dimensions of the fine pattern width on the wafer displayed on the image display unit, the size of the batch, and the like. The effect is that the operator can easily confirm.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a scanning electron microscope of the present invention, FIG. 2 is a diagram showing a CRT display in automatic length measurement by the scanning electron microscope of FIG. 1, FIG. 3, and FIG. FIG. 5 is an explanatory diagram of an application example of the present invention, and FIG. 5 is a diagram showing a CRT display in automatic length measurement by a conventional scanning electron microscope. DESCRIPTION OF SYMBOLS 1 ... Electron source, 2 ... Electron beam, 3 ... Converging lens, 4 ... Deflection coil, 5 ... Objective lens, 6 ... Sample, 7 ... Secondary electron,
8 ... Detector, 9 ... Deflection generator, 10 ... Image memory, 11
... adder, 12 ... cursor generator, 13 ... electronic calculator,
14 ... CRT, 15 ... track ball, 16,17 ... cursor.

Claims (1)

[Claims] 1. A scanning electron microscope which scans a sample with an electron beam, displays a sample image according to a signal generated from the sample, and automatically measures the specified position of the sample. A length measuring means for automatically measuring the length by using an S / N ratio signal obtained by adding and averaging the vertical signals in the length measuring direction and the vertical direction, and a display means for displaying an area to be averaged are provided. A scanning electron microscope characterized by the above.