JPH02165091A - Measurement of beam diameter or beam edge resolution - Google Patents

Abstract

PURPOSE:To enable picking up of an effective signal without being affected by noises by setting an angle theta between a direction of scanning and a tangential to an interface at a value sufficiently less than 90 deg.. CONSTITUTION:An electron beam 7 is deflected with a deflector 1 wherein an applied voltage is changed repeatedly in continuity with a deflection controller 11 with a deflecting voltage controlled by a command from a computer 10 and scans traversing a gold fine line 2 (gold wire 2) so arranged that a diameter position thereof coincides with a height the same as a focal position 3. A relationship between axis-of-abscissa dimensions on a CRT 5 and a moving distance of the electron beam 7 on a focal plane 3 is determined from a thickness (h) of the gold wire 2 and a distance X0 at which a waveform on the CRT 5 traverses 50% at the level thereof. Thus, a beam diameter of the electron beam can be determined by X1/X0h cosec theta. In this case, as a scanning distance is longer by a consec theta factor as compared with the case where the electron beam scans at the right angle of the gold wire 2, higher resolutions are achieved. On the other hand, this results in a larger range of change in a scanning voltage of the deflector 2 thereby making effect of noises hard to suffer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the beam diameter or beam edge resolution of an energy beam with high precision.

[Conventional technology]

Conventionally, when measuring the beam diameter of an energy beam such as an electron beam, the energy beam is scanned in a direction that crosses a certain boundary at a nearly right angle, and the beam diameter is measured from the signal waveform of the energy beam obtained through the boundary. was.

[Problem to be solved by the invention]

However, as the beam diameter becomes smaller, there is a problem that accurate measurements cannot be made with a beam diameter smaller than a certain value due to noise superimposed on the scanning power supply.

An object of the present invention is to provide a method for measuring a beam diameter and beam edge resolution of 0.1 tt m or less with high precision without being affected by scanning voltage, stage vibration, etc.

[Means to solve problems]

Instead of the conventional method of scanning in a direction perpendicular to the boundary, the beam is now scanned in a direction that makes a small angle with the boundary.

That is, in a method of measuring the beam diameter or beam edge resolution of the energy beam from the signal of the energy beam obtained through the boundary when scanning the energy beam across the boundary, the scanning direction and the tangential direction of the boundary This is a method for measuring beam diameter or beam edge resolution, characterized in that the angle θ formed between the beam diameter and the beam edge resolution is set to be an angle sufficiently smaller than 90 degrees.

[For production]

In the present invention, from the time one end of the beam starts touching the boundary until the other end of the beam leaves the boundary, a longer distance is scanned than when scanning at right angles, so the scanning period is longer and the influence of noise is reduced. It is possible to extract a valid signal without receiving any signal.

〔Example〕

FIG. 2 is an embodiment of an apparatus for carrying out the method of the invention. An electron beam 7 focused by an electron optical system (not shown) is deflected by a deflector 1 whose applied voltage is continuously and repeatedly changed by a deflection control device 11 whose deflection voltage is controlled by a command from a computer 10, and the focus position is A thin gold wire 2 (hereinafter referred to as "gold wire 2") is scanned across a thin gold wire 2 (hereinafter referred to as "gold wire 2"), which is provided so that its diameter position coincides with the height of the gold wire 3. However, as shown in FIG. 1, if the angle between the gold wire 2 and the scanning direction is θ degrees, the angle is θ×90. That is, if the gold wire 2 is in the X direction of electron beam scanning, the computer 1o applies a linearly varying signal to the Y direction deflector of the deflector 1, while applying a linearly changing signal to the X direction deflector corresponding to the angle θ. Apply a signal that changes over time. An electron beam detector 4 having a sufficiently larger area than the gold wire 2 is provided below the gold wire 2 at a sufficiently high position, and the electric signal from the detector 4 is processed by image processing controlled by instructions from the computer 10. After being input to the device 12 and amplified, it is stored in the image memory as a one-dimensional image signal synchronized with the scanning of the deflector 1. ,
A waveform as shown in FIG. 3 is displayed on the CRT 5.

Conventional circuits and operations can be used as they are. Therefore, the size h of the gold wire 2 and the distance XO at which the waveform on the CRT 5 crosses 50% of its level (this is
The relationship between the horizontal axis dimension on the CRT 5 and the moving distance of the electron beam 7 on the focal plane 3 is determined from Desired. Therefore, the beam diameter of the electron beam is the horizontal axis distance X where the waveform on the CRT 5 changes from 90% to 10%.

, it is determined by −h cosec θ. In other words, in the above embodiment, the scanning distance is cosecθ times longer than when scanning at right angles to the gold wire 2 (therefore, the resolution is improved. By the way, the horizontal axis distance on CRTs corresponds to the scanning voltage, so as the scanning distance becomes longer, the time from when the beam hits the gold wire 2 to when it is completely hidden increases, so the range of change in the scanning voltage of the deflector 2 during that time increases. Therefore, it is difficult to be affected by noise.

Note that normally, it is preferable to have the computer 10 calculate the beam diameter based on an image signal stored in the image memory of the image processing device 12, rather than determining the beam diameter from the screen on the CRTS. That is, the computer 10 first obtains the maximum value and minimum value of the one-dimensional image signal from the image memory of the image processing device 12, and calculates the interval between the falling part and the rising part where the image signal becomes 50%, for example, in the image. Number of pixels in memory n. The size h of the gold wire 2 given in advance is calculated by
And from the angle θ between the scanning direction and the longitudinal direction of the gold wire 2,
Distance h c on focal position 3 per pixel of image memory
Calculate osec θ/no. Then, calculate the interval (corresponding to Number of pixels in image memory nl
The distance per pixel h cosec θ/
From n0 and the number of pixels n, calculate nl -h C08e
The beam diameter is determined by Cθ/no, and this beam diameter is displayed on the CRT 5.

Note that the gold wire 2 described above can be replaced with a metal wire with no unevenness on the surface, or can be replaced with a border with a level difference or the like. Furthermore, it goes without saying that the beam diameter of other energy beams can be similarly measured instead of the electron beam.

In addition, Xt in FIG. 3 corresponds to the edge resolution that represents the degree of blur in the peripheral part of the beam, and xt can be easily obtained from the signal obtained by differentiating the waveform in FIG.
The true beam resolution can be calculated in the same way as when calculating the beam diameter.

〔Effect of the invention〕

According to the present invention as described above, the variation width of the scanning voltage is multiplied by cosecθ compared to the case of scanning perpendicular to the boundary, so conversely, when the beam resolution is determined by the noise of the scanning voltage, Measurements can be made up to a beam diameter that is θ times smaller.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the gold wire and the scanning direction, FIG. 2 is a schematic diagram of an apparatus for carrying out the method of the present invention, and FIG. 3 is a diagram showing the relationship between the gold wire and the scanning direction.
This is an example of an image displayed on RT. (Explanation of symbols of main parts) 2...Gold wire, 6...Scanning direction, 7...Electron beam Applicant: Nikon Corporation

Claims (1)

[Claims] In the method of measuring the beam diameter or beam edge resolution of the energy beam from the energy beam signal obtained through the boundary when the energy beam is scanned across the boundary, the scanning direction and the tangential direction of the boundary A method for measuring beam diameter or beam edge resolution, characterized in that the angle θ formed by is made sufficiently smaller than 90 degrees.