JP3221984B2 - Evaluation method for electron beam writing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam writing 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 With the advance of semiconductor technology, higher speed and higher integration of semiconductor devices have been promoted. Along with this, the necessity of pattern miniaturization is increasing,
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 using an optical stepper which has been widely used in the past, and there is a strong demand for a lithography means capable of forming a pattern with high precision.

[0004] Among them, electron beam lithography is receiving attention as the most influential method. In the electron beam lithography, a variable shaped beam (VSB) method has been adopted for the purpose of improving the throughput.

FIG. 1 shows an example of a schematic configuration diagram of an electron beam writing apparatus using a VSB system. In the figure, reference numeral 11 denotes an electron gun, and an electron beam emitted from the electron gun 11 is applied to a first beam shaping aperture mask 14 by two condenser lenses 12 and 13. The image formed by the aperture 14a of the first aperture mask 14 is projected onto a second beam shaping aperture mask 16 by a projection lens 15. 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, between the reduction lens 17 and the objective lens 18, scanning deflectors 21 and 22 are arranged. These deflectors 21 and 22 scan the beam on the sample surface 19. Further, the first aperture mask 14 and the projection lens 15
A beam shaping deflector 23 is disposed between the two.
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 drawing, reference numeral 31 denotes an image formation state of the electron gun crossover, and reference numeral 32 denotes an image formation state of the aperture.

In such a VSB method, a beam formed into various dimensions is connected to form a pattern. Therefore, in order to draw a high-precision and good pattern, it is necessary to adjust the beam dimension with high precision. is there.

Therefore, various techniques have been attempted for adjusting a beam shift caused by a slight shift of an optical lens barrel or a control portion of a drawing apparatus and evaluating a pattern under a certain standard.

However, even when a beam that should have been ideally adjusted is used, the drawn pattern is not always formed ideally. If the pattern is not idealized, it is not. What caused the problem could not be easily and sufficiently accurately evaluated.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method which can easily classify and evaluate factors of accuracy deterioration in a drawn pattern and can perform the method with high accuracy. The purpose is to:

[0011]

According to the present invention, as an evaluation pattern, a vertical line and a horizontal line pattern formed by sequentially joining rectangular beams having different lengths, and a divided rectangular beam having the same width are combined. By observing the pattern shapes of the vertical and horizontal line patterns formed by sequentially changing the width, it is possible to classify and evaluate the factors that cause the accuracy deterioration of the rectangular beam.

[0012]

According to the present invention, factors that degrade the drawing accuracy of a rectangular beam can be easily classified and evaluated in a short time.
As a result, high-precision drawing becomes possible by individually adjusting the clarified factors.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for evaluating an electron beam according to an embodiment of the present invention will be described in detail with reference to the drawings. First, as shown in FIG. 2, an evaluation pattern 40 composed of rectangular beams having different lengths is input to a writing control device as writing data, and an acceleration voltage of 15 kV and a current density of 10 A are applied by the electron beam to be evaluated. / cm2, irradiation dose 4μC
Draw on the positive resist (EBR-9) film applied to the surface of the chrome-coated quartz glass substrate (mask) under the condition of / cm2, and develop for 4 minutes and 15 seconds using MIBK (methyl isobutyl ketone). went. Where the pattern width of each evaluation pattern is
2.0μm and beam length from 2.5μm to 0.25μ respectively
It is composed of a rectangular beam changed in steps of 0.25 μm to m.

At the time of evaluation, by comparing and observing how the pattern shape of each pattern, in particular, the shape of the connecting portion of the beam, changes, the displacement of the optical lens barrel or the control portion with respect to the rectangular beam, in particular, Evaluation of the molding deflection sensitivity can be performed.

[0015] SEM observation of the roughness at the joint of the rectangular beams of the formed pattern was performed. As a result, the roughness was almost 0 μm for both the vertical line and the horizontal line pattern when the beam length was 0.25 μm, but increased as the beam length increased. At a beam length of 2.5 μm, the vertical line pattern was approximately 0.1 μm and the horizontal line pattern was approximately 0.05 μm. μ
m. From this, it can be seen that the ratio of the change in the actual beam length to the change in the set beam length, that is, the forming deflection sensitivity is not ideal, and that the deviation is different between the vertical line pattern and the horizontal line pattern. Therefore, by making adjustments to eliminate this shift,
A good pattern can be formed with high accuracy regardless of the pattern size. Furthermore, qualitative evaluation can be easily performed using an optical microscope.

Similarly, as shown in FIG. 3, a pattern composed by dividing into rectangles having the same width and sequentially changing the width is drawn. Here, the pattern width of each evaluation 41 was 2.0 μm, the beam length was fixed at 2.5 μm, and the beam width was 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. At the time of evaluation, by comparing and observing the pattern size of each pattern, it is possible to evaluate the shift of the optical lens barrel or the control portion with respect to the rectangular beam, particularly the offset of the beam current.

After developing the pattern thus drawn, the pattern dimensions were measured from an SEM photograph. As a result, in the pattern divided by the beam width of 0.1 μm, the vertical line pattern is formed to be 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. Was. This is because the pattern must be formed in the same way when drawing with a 2.0 μm beam and when drawing with 0.1 μm divisions. It can be seen that the horizontal line pattern shifts in the direction in which the current increases and in the direction in which the horizontal line pattern decreases. By adjusting this shift, it is possible to ideally perform pattern formation even when a minute beam is used.
Furthermore, qualitative evaluation can be easily performed using an optical microscope. Also, regarding the orthogonality of the two apertures forming the beam, such a state appears remarkably by drawing by increasing the number of divisions of the beam as described above. Evaluation can be easily performed.

In the embodiment of the present invention, two types of evaluation patterns are used as shown in FIGS. 2 and 3, but it is apparent that a pattern obtained by combining these two types may be used. By using the evaluation patterns 42 and 43 as shown in FIGS. 4 and 5, it is possible to evaluate a triangular beam similarly to a rectangular beam.

[0019]

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

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an evaluation pattern according to the embodiment of the present invention.

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

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

FIG. 5 is a diagram showing an evaluation pattern according to 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 Yasuse 1 Toshiba R & D Center, Komukai Toshiba-cho, Saisaki-ku, Kawasaki-shi, Kanagawa Prefecture (56) References JP-A-59-135728 (JP, A) JP-A-60-182725 (JP, A) JP-A-55-88329 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027

Claims (2)

(57) [Claims] 1. An electron beam writing evaluation for irradiating an aperture mask having a predetermined opening shape with an electron beam to form a beam having the opening shape and thereby evaluating a pattern drawn on a substrate to be processed. In the method,
As an evaluation pattern, a vertical line and a horizontal line pattern formed by sequentially joining rectangular beams of different lengths are combined with the divided rectangular beams having the same width, and the vertical lines formed by sequentially changing the width. An electron beam writing / evaluating method characterized in that a pattern shape of a horizontal line pattern can be observed to classify and evaluate accuracy deterioration factors of a rectangular beam. 2. An electron beam writing evaluation for irradiating an aperture mask having a predetermined aperture meter with an electron beam to form a beam of the aperture meter and thereby evaluating a pattern written on a substrate to be processed. In the method,
As an evaluation pattern, a vertical line and a horizontal line pattern formed by sequentially joining rectangular beams of different lengths are combined with the divided rectangular beams having the same width, and the vertical lines formed by sequentially changing the width. By observing the pattern shape of the horizontal line pattern, it is possible to classify and evaluate the accuracy deterioration factors of the rectangular beam, and to clarify the accuracy deterioration factors such as shaping deflection sensitivity, beam current offset or aperture orthogonality. An electron beam writing / evaluating method characterized by individually adjusting.