JPS58186009A - Measuring method of length - Google Patents

Abstract

PURPOSE:To measure pattern line width or line interval with high accuracy, by slightly moving a material in the measuring direction, scanning a charge particle beam when said material is moving, and measuring a distance between desired two points and a moving extent of the material. CONSTITUTION:A command for moving a material stage 10 in the pattern line width measuring direction, and a command for digitally scanning a beam in the X direction on a material are sent to a motor controlling circuit 11 from a CPU6, and the same part on the material 4 is digitally scanned plural times when the stage 10 is moving. When each scanning beam crosses the edge of a pattern P0, a reflecting electronic signal is inputted to the CPU6, the CPU6 relates this signal to a digital scanning signal, A corresponding to a moving distance of the stage 10 and B corresponding to a distance between edges of the pattern P0 are detected, and simultaneously, L corresponding to the moving distance of the stage 10 is measured by a laser measuring instrument 12. As for the measured value L, its reliability is high as 2X10<-7>m, A is calculated in terms of the measured value L, B is calibrated, and line width of the pattern P0 is calculated with high accuracy by operation of B/AXL.

Description

[Detailed description of the invention] The present invention relates to a sub-length method using a charged particle beam.

In the manufacturing process of LSI devices and ultra-T-SR devices, pattern inspections such as measuring the line width and line spacing of patterns created on materials are performed. Since the line widths of these patterns reach the micron level, it is impossible to measure them optically.

Therefore, it is conceivable to use an electron beam or an ion beam to measure the line width and other sub-lengths. In other words, by digitally scanning a charged beam over a material and capturing reflected electrons emitted from the material, the positions of the lines and irregularities to be measured are detected. The line width and line spacing are measured in relation to the digital scanning. However, in general, the material itself has displacements such as warping and unevenness, and the material stage also has similar displacements and backlash during horizontal movement, so the work distance may vary within and between materials. occurs, resulting in incorrect length measurement. FIG. 1 shows an example of this, in which pattern line widths are measured at different workpiece distances in the same material M, and a pattern P formed at a workpiece distance D is shown. line width and work distance D
The line width of the pattern P', which has the same line width as the pattern P formed at the location ', is directed by the deflector DF to the beam B
By digitally scanning in the direction and sub-lengthening each line width, the line width of pattern P is obtained corresponding to the movement (deflection) angle α of the beam from edge to edge of one pattern, and the line width of pattern P' is obtained. obtains the number corresponding to α′ (〈α). However, even if α and α' can be known, the line width cannot be calculated unless the work distances D and D' are known.

Further, it is generally difficult to determine the work distance D, I')' with high precision. As a result, a measurement error corresponding to (α-α') occurs even though the same line width is measured. This error is a serious problem when measuring line widths in submicron units.

The present invention has been made in view of these points, and relates to a novel length measuring method that allows the line width and line spacing of a pattern to be accurately measured without knowing the workpiece distance.

Now, the beam is moved by a predetermined amount in the direction of the sub-length, while the beam is digitally scanned over the material. Measure the line width of the pattern (set the length measurement value to b) and the amount of movement of the monthly interest rate (set all + list price to a), and at the same time measure the amount of movement of the monthly interest rate using a laser length measurement system (measure The ratio of the pattern line width measurement value 1) to the material movement height measurement value a multiplied by the monthly rate of movement m measured by the laser length measurement system is the value of the laser length measurement system. The pattern line width value depends on reliability. If the line widths are the same, the ratio of the pattern line width measurement value b' obtained by digital scanning of the beam of the pattern at different work distances to the abrasive movement measurement value a' is the ratio b/ Same as a. Therefore, if the line width is the same, the same pattern line width value will be measured regardless of the work distance. Furthermore, this length measurement value is highly accurate due to the reliability of the laser length measurement system. The present invention is based on such a principle, in which the material is moved by a small amount in the direction of the sub-length, and at least a plate-spinning charged particle beam is scanned over the material between the start of movement and the time of stop of movement. Based on the signal detected from above, the desired distance between two points on the material and the movement m of the material 3-size are measured in relation to the scanning, and when the material is moved, the amount of movement is measured using a laser length measuring system. Convert the amount of movement of the material measured in relation to the scanning with the value determined by the laser length measurement system, and calculate the line width or line of the measured pattern based on the converted value. A new/r length measurement method with calibrated spacing is provided.

FIG. 2 shows an embodiment of the present invention.

In the figure, reference numeral 1 denotes an electron gun, and an electron beam emitted from the electron gun is focused by electron lenses 2 and 3 onto a material 4 on which a pattern (including patterns such as marks) is formed. Reference numeral 5 denotes a deflector, and usually a pair of deflectors are provided, one for scanning in the X direction and the other for scanning in the Y direction.

The deflector is actuated by a digital scanning signal sent from a digital scanning signal generation circuit 7 which is actuated by a command from a central processing unit (called CPU) 6, and uses an electron beam.
Scan on 4. Reference numeral 8 denotes a backscattered electron detector, which detects backscattered electrons generated from the material 4 by the scanning. 9 is a motor for moving the material stage 10, and the CPU 6
It is controlled by the Saturday-to-evening control circuit 11 which is activated in response to a command. A laser length measuring device 12 detects the amount of movement of the material stage 10, and sends the detected value to the CPU 6.

First, the embodiment shown in FIG. 2 is operated as follows.

First, the CPU 6 sends a command to the motor control circuit 11 to move the material stage 10 in the pattern line width measuring direction (for example, the Sends a command to digitally scan in the X direction. At this time, as shown in FIG. 3, while the material stage 10 moves ten doors, the same location on the material 4 is digitally scanned multiple times. When the beam crosses an edge of the pattern PO in each scan, a backscattered electron signal having information about the edge is sent to the CPU 6 via the backscattered electron detector 8.
Enter. The CPU correlates this signal with the digital scanning signal to generate patterns A and P corresponding to the distance moved by the material stage 10.

Detect B corresponding to the distance between the edges.

4(a), (b) and (0) respectively show the signals detected by the CPU 6 during the first beam scanning before the material stage 10 starts or after the material stage 10 starts moving, and the signals detected by the first beam scanning [1]. The detected signal is a signal detected by the last beam scan, and is due to the detection of the edge portion of the pulse-like portion [;1 pattern PO. Incidentally, △ corresponding to the distance traveled by the +1 size stage 10 detected in this way and B corresponding to the distance between edges of the pattern Pa are detected as the number of digital scanning steps. . Now, while Δ and B are detected in this way, at the same time,
The laser length measuring device 12 measures J, which corresponds to the movement of the material stage 10 (1-). Laser length measuring device 1
The value 1- measured by 2 has a very high reliability of 2×10-7 m. Therefore, the CPU 6 converts the △ corresponding to the moving part of the material stage 10 detected in relation to the digital scanning with the value measured by this highly reliable laser length measuring device 12, and converts it into Based on the value, the distance between the edges of the pattern PO detected in relation to the digital scanning, that is, the distance B corresponding to the line width of the pattern Po is calibrated. That is, a highly accurate line width of the pattern PO is calculated by calculating B/Δ×l−.

It should be noted that the CPU 6 receives the signal from the material 4 during the first beam scan and the signal from the material 114 during the last beam scan immediately before the removal stage 10 starts moving or from the time it starts moving until it stops. Since it is sufficient if the signal is obtained, the signal from the material 4 due to intermediate beam scanning may be automatically ignored.

According to the present invention, it is possible to measure the pattern line width or line spacing with high precision without knowing the workpiece distance, depending on the reliability of the laser length measurement system.

[Brief explanation of drawings]

Fig. 1 shows a sub-length method using electron beam scanning on a material1), Fig. 2 shows an embodiment of the present invention, and Figs. 3 and 4 show the operation of the embodiment shown in Fig. 2. This is used to supplement the explanation. 4: Month 1'31.5: Deflector, 6: Central processing unit (CP
LJ), 7: Digital scanning signal generation circuit, 8: Foul electron detector, 10: Material stage, 12: Laser length measuring device.

Claims (1)

[Claims] The material is moved by a small amount in the length measurement direction, and at least a plate-spinning charged particle beam is scanned on the material between the start of the movement and the time of the stop of the movement, and the signals detected from the material by the scanning are related to the scanning. Measure the desired distance between two points of material 1- and the amount of movement of the material, measure the amount of movement with a laser length measurement system when moving the material, and measure the amount of movement of the material measured in relation to the scanning. A sub-length method in which a value measured by the laser length measurement system is converted, and the line width or line spacing of the measured pattern is calibrated based on the converted value.