JPH09251939A - Method of adjusting electron beam plotting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a beam with little deviation of the charge distribution in a pattern by detecting the offset of the beam size and gain wherein the reflection waveform at the edge of a thin rectangular pattern agrees with that at the edge of a bold rectangular pattern to set an optimum beam size. SOLUTION: A resist is coated on a work, a rectangular pattern divided into a thin and bold rectangular patterns 1 and 2 is formed by plot-scanning a very small and large size beams on the resist with changing the offset of the beam size and gain one by one and reflected signals are measured. From these signals, the offset of the beam size and gain are detected to obtain an optimum beam size in which the reflection waveform at the edge of the pattern 1 agrees with that at the edge of the pattern 2, thereby obtaining a beam with little deviation of the charge distribution in the pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting an electron beam drawing apparatus, and more particularly to a method for forming a highly accurate exposure pattern in a variable shaped electron beam drawing apparatus.

[0002]

2. Description of the Related Art In a variable shaping type electron beam drawing apparatus, a pattern is drawn by changing the cross-sectional shape and size of an electron beam (hereinafter referred to as a beam) according to the shape and size of a pattern drawn on a target. Therefore, the pattern can be drawn at high speed and with high accuracy.

As a method for determining the beam size in this drawing method, a beam shaped to a set size is scanned over metal particles, the intensity distribution of the beam is determined from the reflected electron signal obtained at this time, and the beam is calculated from the intensity distribution. It is known how to determine the dimensions of. If the dimension determined by this method is regarded as the actual dimension, the relationship between the set dimension of the beam and the actual dimension can be approximated by a linear function. FIG. 4 shows the relationship between the set dimensions of the beam and the actual dimensions. The y-intercept Q in FIG. 4 represents the beam offset, and the slope of the straight line represents the beam gain. The broken line in FIG. 4 represents the ideal state. Since it is desirable that the set size and the actual size of the beam match, the gain and offset of the amplifier of the shaping deflector are corrected by a command from the CPU so that the relationship shown by the broken line in FIG. 4 is obtained. ing.

[0004]

When the beam size becomes extremely small, it becomes difficult to generate a stable beam, and it becomes difficult to measure the beam size. Furthermore, when a pattern is drawn by connecting beams with extremely different beam dimensions, the bias in the charge distribution within the pattern becomes noticeable, and there are problems such as increased pattern roughness at the beam connection boundary and varying dimensions. Occurs.

In view of the above problems, the present invention provides a variable shaping type electron beam drawing apparatus in which even if the beams are drawn by connecting the beams having extremely different beam sizes, the bias of the charge distribution in the pattern is small. It is an object of the present invention to provide a beam size adjusting method capable of obtaining the following.

[0006]

In order to solve the above problems, the present invention provides a rectangular pattern divided into a thin rectangular pattern drawn by a beam of a small size and a thick rectangular pattern drawn by a beam of a large size. Drawing with various offsets and gains of the beam size, developing the pattern, measuring the reflected light by scanning the pattern with a laser beam or the like, and tilting the reflected waveform at the edge of the thin rectangular pattern and Provided is an adjusting method of an electron beam drawing apparatus, which makes an offset and a gain of a beam size that make the inclination of a reflected waveform at an edge of a thick rectangular pattern equal to each other.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an example of a pattern used in the present invention. 2A shows a rectangular pattern drawn with the maximum beam size, and FIG. 2B shows a rectangular pattern drawn by connecting a minute beam having a width l1 and a beam having a width l2.
It is a rectangular pattern having the same dimensions as (a). Here, l1 << l2.

A plurality of patterns shown in FIG. 2 (b) are drawn on a positive resist coated on a workpiece, for example, while changing the beam size offset and gain at regular intervals. FIG. 3 shows a layout example of a pattern in which the beam size offset and gain are changed. In FIG. 3, the offset and the gain are centered around 0, and p and
The pattern is exposed by changing the interval and the q interval.

After the pattern is drawn, the exposed resist is developed in a time shorter than the optimum development time so that the bottom of the resist is present on the material to be processed. FIG. 1 (a), (b)
[FIG. 4] is a view of the developed pattern as seen from above. 1 is
A pattern drawn by a beam having a small size is shown, 2 is a pattern drawn by a beam having a large size, and a broken line 3 is a boundary line between both patterns. If the charge density of the small size beam and the charge density of the large size beam are equal and the charge distribution in the pattern is uniform, the pattern 1 shot with the small size beam and the pattern 2 shot with the large size beam
Are developed at the same speed, so that they are developed into the shape shown in FIG. On the other hand, if the charge density of the minute size beam is smaller than the charge density of the large size beam and the charge distribution in the pattern is non-uniform, the development speed of the pattern 1 shot by the minute size beam is large. Since the developing speed of the shot pattern 2 is slower, it is developed into the shape shown in FIG.

Next, the patterns of these developed resists are scanned with, for example, a laser beam or an electron beam,
The reflected light is measured. FIG. 1C shows a reflection waveform when the pattern of FIG. 1A is scanned left and right in the drawing,
FIG. 1D shows a reflection waveform when the pattern of FIG. 1B is scanned left and right. Since the irradiation light is strongly scattered at the edge portion of the resist, the measurement light is weak. If the charge distribution in the pattern is uniform as shown in FIG. 1A, the shape of the edge of the pattern is almost the same on the left and right sides, so that a symmetrical reflection waveform is obtained as shown in FIG. 1C. . On the other hand, FIG.
When the left and right edges shown in (b) have different charge distributions, the left and right developing speeds are different, so that the reflected waveforms are different between the left and right as shown in FIG. Therefore, by observing the reflection waveform, as shown in FIG. 1C, the reflection waveform at the edge shot with the minute beam and the reflection waveform at the edge shot with the large size beam are the same. It suffices that the optimum offset value and the optimum gain of the electron beam apparatus are set to the optimum offset value and the optimum gain.

Therefore, for example, a pattern group as shown in FIG. 3 is scanned with laser light, and the reflected light is measured, and the pattern shown in FIG.
The offset and the gain of the pattern in which the reflection waveform as shown in (c) is obtained may be the optimal offset value and the optimal gain.

The analysis of these reflection waveforms and the determination of the optimum value can be automatically performed. Furthermore, although the positive type resist is used in the above description, it is not limited thereto.

[0013]

As described above, according to the present invention,
Since the charge density of the small size beam and the charge density of the large size beam are equal, the charge distribution in the pattern becomes uniform in the pattern drawn by connecting the small size beam and the large size beam, and the pattern is disturbed. It is possible to prevent dimensional variation.

[Brief description of drawings]

FIG. 1 is a diagram showing a development pattern obtained by the present invention and a reflection waveform when the pattern is scanned with a laser beam.

FIG. 2 is a diagram showing a rectangular pattern used in an embodiment of the present invention.

FIG. 3 is a layout diagram of patterns used in an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a set dimension of an electron beam and an actual dimension.

[Explanation of symbols]

 1 ... A pattern drawn with a minute rectangular beam, 2 ... A pattern drawn with a large rectangular beam, 3 ... A boundary line.

Claims (2)

[Claims] 1. When adjusting the relationship between the set dimension and the actual dimension of a beam in a variable shaped electron beam apparatus, a resist is coated on a workpiece, and a narrow rectangular pattern and a large dimension are drawn by a beam with a minute dimension. One rectangular pattern divided into thick rectangular patterns to be drawn with the beam is drawn on the resist by sequentially changing the offset and gain of the beam size, the resist pattern is developed, the resist pattern is scanned, and its reflection signal is obtained. Is measured to detect the offset and gain of the beam size at which the reflection waveform at the edge of the thin rectangular pattern and the reflection waveform at the edge of the thick rectangular pattern match, and to determine the optimum offset and gain of the beam size. Adjusting method of electron beam writer. 2. The resist is a positive type resist,
2. The method of adjusting an electron beam drawing apparatus according to claim 1, wherein the pattern is developed in a time shorter than an optimum developing time, and the resist is left on the workpiece even in an exposed portion.