JPH0750248A - Electron beam lithograph evaluating method - Google Patents

Abstract

PURPOSE:To enable the causing factor of deteriorated precision in rectangular beams to be evaluated by classification by a method wherein the rectangular beams of the same width are assembled together for successively changing the width thereof to make an observation of the shapes of vertical and horizontal line patterns. CONSTITUTION:Firstly, evaluation patterns 40 composed of rectangular beams in different lengths as beam exposure data are inputted in a beam exposure control device to be beam-exposed for development on a posiresist film applied on the surface of a quartz glass substrate by electron beams for evaluating the evaluation patterns 40. At this time, respective evaluation patterns 40 in a specific pattern width of 2.0mum are composed of rectangular beams in variable beam lengths within the range of 2.5mum-0.25mum at the interval of 0.25mum. Furthermore, the shapes of respective patterns, especially the variation of the shapes in the joint part of beams are comparatively observed. Through these procedures, the slips in optical tube or control part from the rectangular beams, espacially the molding deflection sensitivity can be evaluated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam drawing evaluation method, and more particularly to a method for evaluating a semiconductor integrated circuit pattern such as an LSI drawn on a sample such as a mask or a wafer by an electron beam.

[0002]

2. Description of the Related Art As semiconductor technology has advanced, semiconductor devices have been made faster and more highly integrated. Along with this, the need for finer patterns continues to grow,
High-precision pattern formation has been required for line widths of 0.25 μm and 0.1 μm.

In such a fine device, it is difficult to form a pattern by an optical stepper that has been widely used in the past, and there is a strong demand for a lithographic means capable of forming a highly precise pattern.

Among them, the electron beam lithography is drawing attention as the most effective method. In the electron beam lithography, a variable shaped beam (VSB) method has been adopted for the purpose of improving throughput.

FIG. 1 shows an example of a schematic configuration diagram of an electron beam drawing apparatus using the VSB method. In the figure, 11 is an electron gun, and the electron beam emitted from this electron gun 11 is applied to the first beam shaping aperture mask 14 by the two condenser lenses 12 and 13. The image of the aperture 14a of the first aperture mask 14 is projected by the projection lens 15 onto the second beam shaping aperture mask 16. The image of the aperture mask 16a of the second aperture mask 16 is formed on the sample surface 19 by the reduction lens 17 and the objective lens 18.

Further, scanning deflectors 21 and 22 are arranged between the reduction lens 17 and the objective lens 18. These deflectors 21 and 22 scan the sample surface 19 with the beam. Also, the first aperture mask 14 and the projection lens 15
A beam-forming deflector 23 is arranged between and.
The deflector 23 changes the image position of the first aperture 14a on the second aperture mask 16 and changes the size and shape of the beam irradiated and imaged on the sample surface 19. In the figure, 31 indicates the image formation state of the electron gun crossover, and 32 indicates the image formation state of the aperture.

In such a VSB method, since beams formed in various sizes are connected to form a pattern, it is necessary to adjust the beam size with high accuracy in order to draw a good pattern with high accuracy. is there.

Therefore, various methods have been tried for adjusting the deviation of the beam caused by a slight deviation of the optical lens barrel or the control portion of the drawing apparatus to evaluate the pattern under a certain standard.

However, even when the beam that should have been adjusted ideally is used, the drawn pattern is not always ideally formed, and if it is not ideal on the pattern, it is It has not been possible to easily and sufficiently accurately evaluate what is causing it.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method capable of easily and highly accurately classifying and evaluating accuracy deterioration factors in a drawn pattern. The purpose is to

[0011]

In the present invention, a vertical line and horizontal line pattern formed by successively connecting rectangular beams of different lengths and a divided rectangular beam of the same width are combined as an evaluation pattern. By observing the pattern shape of the vertical line and horizontal line patterns formed by sequentially changing the width, the factors that cause the accuracy deterioration of the rectangular beam can be classified and evaluated.

[0012]

According to the present invention, the factors that deteriorate the drawing accuracy of the rectangular beam can be easily classified and evaluated in a short time.
As a result, highly accurate drawing becomes possible by individually adjusting the revealed factors.

[0013]

Embodiments of the electron beam evaluation method according to the present invention will be described in detail below with reference to the drawings. First, as shown in FIG. 2, an evaluation pattern 40 composed of rectangular beams having different lengths is inputted to the drawing controller as drawing data, and the accelerating voltage is 15 kV and the current density is 10 A depending on the electron beam to be evaluated. / cm2, irradiation dose 4μC
Draw on the positive resist (EBR-9) film applied on the surface of the quartz glass substrate (mask) coated with chromium under the condition of / cm2, and develop for 4 minutes and 15 seconds using MIBK (methyl isobutyl ketone). went. Here, the pattern width of each evaluation pattern is
2.0 μm, beam length from 2.5 μm to 0.25 μm
It is composed of a rectangular beam which is changed to m by the step of 0.25 μm.

In the evaluation, by comparing and observing how the pattern shape of each pattern, especially the shape of the beam connecting portion, changes, the deviation of the optical lens barrel or the control portion with respect to the rectangular beam, especially, The molding deflection sensitivity can be evaluated.

In this way, SEM observation of the roughness in the connecting portion of the rectangular beams of the formed pattern was performed. As a result, the roughness was about 0 μm for both the vertical and horizontal lines when the beam length was 0.25 μm, but increased as the beam became longer, and the vertical line pattern was about 0.1 μm and the horizontal line pattern was about 0.05 when the beam length was 2.5 μm. μ
It became m. From this, it can be seen that the ratio of the actual change of the beam length to the change of the set beam length, that is, the shaping deflection sensitivity is not ideal, and the deviation is different between the vertical line pattern and the horizontal line pattern. Therefore, by adjusting to eliminate this deviation,
It is possible to perform high-precision and good pattern formation in any pattern size. Furthermore, qualitative evaluation can be easily performed using an optical microscope.

Similarly, as shown in FIG. 3, the pattern was divided into rectangles having the same width, and the width was sequentially changed to draw a pattern. The pattern width of each evaluation 41 is 2.0 μm, the beam length is fixed at 2.5 μm, and the beam widths are 2.0 μm, 1.0 μm, and 0.5 μm, respectively.
It is composed of rectangular beams of m, 0.25 μm, and 0.1 μm. In the evaluation, by comparing and observing the pattern dimensions of the respective patterns, it is possible to evaluate the deviation of the optical lens barrel or the control portion with respect to the rectangular beam, especially the offset of the beam current.

After developing the drawn pattern in this manner, the pattern dimension was measured from the SEM photograph. As a result, in the pattern divided by the beam width of 0.1 μm, the vertical line pattern is formed about 0.2 μm thicker than the pattern drawn by the beam of 2.0 μm width, while the horizontal line pattern is not formed due to insufficient irradiation amount. It was This is because the pattern must be formed in the same way when the beam is drawn with a beam of 2.0 μm width and when it is divided into 0.1 μm. It can be seen that the horizontal line pattern deviates in the direction in which the current increases and decreases in the direction in which the current increases. By adjusting this deviation, it is possible to ideally form a pattern even when a minute beam is used.
Furthermore, qualitative evaluation can be easily performed using an optical microscope. In addition, regarding the orthogonality of the two apertures forming the beam, the state becomes conspicuous by drawing by increasing the number of divisions of the beam in this way, and even if an optical microscope is used. It is possible to easily evaluate.

In the embodiment of the present invention, two kinds of evaluation patterns are used as shown in FIGS. 2 and 3, but it is obvious that a combination of these patterns may be used. Further, by using the evaluation patterns 42 and 43 as shown in FIGS. 4 and 5, it is possible to evaluate a triangular beam in the same manner as a rectangular beam.

[0019]

As described above, according to the present invention, by observing the pattern shape of vertical line and horizontal line patterns as the evaluation pattern, it is possible to easily classify and evaluate the factors of accuracy deterioration of the shaped beam in a short time. In addition, it is possible to perform highly accurate drawing by individually adjusting the revealed accuracy deterioration factors.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an electron beam drawing apparatus.

FIG. 2 is a diagram showing an evaluation pattern of an example of the present invention.

FIG. 3 is a diagram showing an evaluation pattern of another embodiment of the present invention.

FIG. 4 is a diagram showing an evaluation pattern of another embodiment of the present invention.

FIG. 5 is a diagram showing an evaluation pattern of another embodiment of the present invention.

[Explanation of symbols]

 14 First Beam Forming Aperture Mask 14a Aperture 16 Second Beam Forming Aperture Mask 16a Aperture 40 Evaluation Pattern 41 Evaluation Pattern 42 Evaluation Pattern 43 Evaluation Pattern

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroto Anse 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Incorporated Toshiba Research and Development Center

Claims (2)

[Claims] 1. An electron beam drawing evaluation for evaluating a pattern drawn on a substrate to be processed by irradiating an aperture mask having a predetermined hole shape with an electron beam to form the beam having the hole shape. In the method
As an evaluation pattern, a vertical line and a horizontal line pattern formed by connecting rectangular beams of different lengths in sequence and a divided rectangular beam of the same width are combined, and a vertical line formed by sequentially changing this width. And an electron beam writing / evaluating method, wherein the factor of accuracy deterioration of the rectangular beam can be classified and evaluated by observing the pattern shape of the horizontal line pattern. 2. An electron beam writing evaluation for evaluating a pattern drawn on a substrate to be processed by irradiating an aperture mask having a predetermined hole opening with an electron beam to form a beam of the hole opening. In the method
As an evaluation pattern, a vertical line and a horizontal line pattern formed by connecting rectangular beams of different lengths in sequence and a divided rectangular beam of the same width are combined, and the vertical line formed by sequentially changing this width. And by observing the pattern shape of the horizontal line pattern, it is possible to classify and evaluate the factor of accuracy deterioration of the rectangular beam, and to clarify the revealed factor of accuracy deterioration such as shaping deflection sensitivity, beam current offset or orthogonality of the aperture. An electron beam drawing evaluation method characterized by being adjusted individually.