JP2910439B2 - Electron beam exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a block exposure method in electron beam exposure. More specifically, the present invention relates to an improvement in an electron beam exposure method for forming a beam by passing through a transmission hole pattern on a stencil mask and reducing and transferring the transmission hole pattern of the stencil mask onto a sample.

2. Description of the Related Art In recent years, as semiconductor elements such as VLSIs have become more highly integrated, there has been a demand for miniaturization of integrated circuit (IC) patterns. Under these circumstances, great expectations are placed on the practical application of electron beam exposure methods with high accuracy.

[0003]

2. Description of the Related Art In a conventional electron beam exposure apparatus,
In most cases, a variable rectangular system is adopted. However, in the variable rectangle method, it is difficult to draw a pattern other than a rectangular pattern. Therefore, in the case of drawing an IC pattern, the so-called one-stroke method is used, but this method has a problem that the throughput does not increase.

To solve this problem, a "block exposure method" has been devised. FIG. 5 is a schematic diagram illustrating a beam path of an electron beam exposure apparatus. In the figure, 1 is an incident mask deflector, a two-stage configuration with eight poles (only two poles are shown in each figure), 2 is a stencil mask, and 3 is an exit mask deflector. A two-stage configuration of poles, 4 is an aperture, 5 is a sample to be exposed, 6 is a stage, 7 is an electron gun, 8 is a slit, 9 is a transmission hole pattern, and 10 is an optical axis. The dotted line represents an example of the electron beam path.

The electron beam emitted from the electron gun 7 is swung by the incident mask deflector 1 so as to pass through a desired transmission hole pattern. The beam that has passed through the stencil mask 2 is returned by the exit mask deflector 3 so as to return to the original optical axis 10, passes through the aperture 4, and forms an image on the sample 5.

As described above, in the block exposure method, several types of transmission hole patterns (
In this method, a beam of a desired pattern is formed by passing a beam through a desired through-hole pattern, and the block pattern is reduced and transferred.

[0007]

In the block exposure method,
To pass the beam through the desired through-hole pattern 9
It is necessary to deflect the beam from the optical axis 10 by a deflector. In this case, the beam is not necessarily a stencil mask 2
Is not necessarily perpendicular. When the beam is incident obliquely, when passing through the transmission hole pattern 9, the beam shape is deformed from the beam shape that should be originally formed.
FIG. 6 is a schematic diagram comparing a transmission hole pattern on the stencil mask and a pattern on the surface of the sample 5 when a beam is obliquely incident. Fig. 6 (a) shows a stencil mask
2 Due to the thickness (depth) of the upper hole pattern,
Fig. 6 (b) shows the pattern on the stencil mask as shown in Fig. 6 (c). The pattern is reduced in one direction.

Generally, the incident angle of a beam changes according to the amount of deflection, and the current density changes according to the change in the incident angle.
For example, when the incident angle is large, the line pattern becomes thin because the specified beam irradiation amount cannot be obtained, or the originally square pattern is distorted into a diamond shape due to oblique incidence, resulting in accurate and accurate exposure. Was impossible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for performing highly accurate block exposure by adjusting an electron beam so as to be perpendicularly incident on a stencil mask.

[0010]

The above object can be attained by the following method. That is, on the stencil mask, there is a mouth that is composed of a rectangle that is composed of rectangles with two orthogonal directions X and Y as the directions of two adjacent sides, and a transmission hole with an aspect ratio of 4 or more is formed in the X and Y directions. Forming a transmission hole pattern by arranging a plurality of transmission electron beams on the substrate, and rotating the incident electron beam about the X direction of the transmission hole pattern as an axis and adjusting the incident angle of the beam so that the sample current becomes a maximum value. Rotating the incident electron beam about the Y direction of the transmission hole pattern as an axis, and adjusting the incident angle of the beam so that the sample current becomes a maximum value.

[0011]

FIG. 1 is a schematic diagram showing a transmission hole pattern (referred to as a normal incidence measurement pattern) on a stencil mask in this embodiment.

The left side of the drawing is an X pattern for adjusting the incident angle around the X-axis direction, and the right side is a Y pattern for adjusting the incident angle around the Y-axis direction. Such a pattern is called a line and space.

In the figure, a quadrilateral 11 indicated by a broken line represents the size of the incident beam. In order to increase the rate of change of the sample current due to the rotation of the incident beam (that is, the S / N ratio), X
It is desirable that several tens or more transmission holes of the pattern or Y pattern are included in the beam size.

In the line and space pattern, the line width is a, and the thickness of the mask (the depth of the transmission hole) is b.
Then, the transmission current value for the incident angle θ (sample current value)
Is (1− (b / a) tanθ) x 100 [%]
It is represented by Therefore, the larger the aspect ratio (b / a) is, the more easily the change amount can be understood. However, (b / a) is set to about 4 due to the technical limitation of mask fabrication. in this case,
For example, if the incident angle is shifted by 1 °, the sample current value decreases by about 7%. On the other hand, the fluctuation rate of the current value (the rate of fluctuation caused by the fluctuation of the beam emitted from the electron gun when the beam is vertically incident) is about 1%, so that the incident angle is 1 °.
A change in the sample current value in the case of deviation can be sufficiently detected.

FIGS. 2A and 2B show vertical incidence measurement patterns.
A pattern as shown in (b) is also possible. FIG. 2A shows a pattern in which a large number of square transmission holes are arranged in the X and Y directions. FIG. 2B shows a pattern in which a large number of L-shaped transmission holes are arranged in the X and Y directions.

In any case, the pattern for measuring vertical incidence is arranged as far as possible on the stencil mask. If the vertical incidence can be adjusted by the vertical incidence inspection pattern at the peripheral part, it is assured that the incident beam is perpendicularly incident on the transmission hole pattern located on the center side of this vertical incidence measurement pattern. Because.

[0017]

Embodiments of the present invention will be described below. Figure
3 is a vertical incidence measurement pattern according to the present invention.
FIG. 7 is a schematic diagram for explaining a method of actually performing normal incidence measurement using the line and space pattern of FIG.

The number of lines and spaces in this pattern is several tens for both the X and Y patterns, and the width of each line and space is 5 μm. The depth of the through-hole is 20 μm and therefore the aspect ratio is 4.

The incident beam size is about one side long.
It is a 400 μm square. Therefore, the beam irradiates about 40 lines simultaneously. As shown in Fig. 3 (a), the beam is deflected by the incident mask deflector 1 to the position of the X pattern,
Light is incident on pattern 12.

As shown in FIG. 3B, the incident mask deflector 1 is adjusted while the sample current value is measured by the ammeter 14. (X
Rotate the incident beam about a direction. 3) As shown in Fig. 3 (c), the sample current value becomes maximum at the position of the incident beam where the incident surface is parallel to the X direction and perpendicular to the stencil mask surface. Next, as shown in Fig. 4 (d), the beam is deflected by the incident mask deflector 1 to the position of the Y pattern,
Light is incident on pattern 13.

As shown in FIG. 4E, the incident mask deflector 1 is adjusted while the sample current value is measured by the ammeter 14. (Y
Rotate the incident beam about a direction. 4) As shown in Fig. 4 (f), the sample current value becomes maximum at the incident beam position where the incident surface is parallel to the Y direction and perpendicular to the stencil mask surface.

In this manner, the adjustment is completed so that the incident beam is perpendicularly incident on the vertical incidence measurement pattern.

[0023]

According to the present invention, there is provided a method which enables highly accurate block exposure by adjusting an electron beam so as to be perpendicularly incident on a stencil mask. As a result, the technology that can respond to the miniaturization of IC patterns, such as VLSI, greatly contributes to the practical use of electron beam exposure.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a transmission hole pattern on a stencil mask in the present embodiment.

FIG. 2 is a view showing another normal incidence measurement pattern;

FIG. 3 is a schematic diagram illustrating a method of performing vertical incidence measurement using the line-and-space pattern of FIG. 1 as a vertical incidence measurement pattern (part 1)

FIG. 4 is a schematic diagram illustrating a method of performing vertical incidence measurement using the line-and-space pattern of FIG. 1 as a vertical incidence measurement pattern (part 2)

FIG. 5 is a schematic diagram illustrating a beam path of an electron beam exposure apparatus.

FIG. 6 is a schematic diagram comparing a transmission hole pattern on a stencil mask and a pattern on a sample surface when a beam is obliquely incident.

[Explanation of symbols]

 1 Incident mask deflector 2 Stencil mask 3 Exit mask deflector 4 Aperture 5 Sample 6 Stage 7 Electron gun 8 Slit 9 Transmission hole pattern 10 Optical axis 11 Beam size quadrilateral 12 X pattern 13 Y pattern 14 Ammeter

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-171808 (JP, A) JP-A-1-217842 (JP, A) JP-A 64-7523 (JP, A) JP-A-5-175 251320 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (4)

(57) [Claims] A stencil mask provided with a plurality of transmission hole patterns for shaping a cross-sectional shape of an electron beam; An electron beam exposure method for reducing and transferring the transmission hole pattern onto the
On the stencil mask, two orthogonal directions X,
It has a mouth that is composed of a rectangle composed of rectangles with Y being the direction of two adjacent sides, and the transmission holes with an aspect ratio of 4 or more are defined as X and
Forming a transmission hole pattern by arranging a plurality of transmission hole patterns in the Y direction, and rotating the incident electron beam about the X direction of the transmission hole pattern and adjusting the incident angle of the beam so that the sample current becomes a maximum value. Step and Y of the transmission hole pattern
Rotating the incident electron beam about the direction as an axis and adjusting the incident angle of the beam so that the sample current becomes a maximum value. 2. The electron beam according to claim 1, wherein the plurality of transmission hole patterns formed by being arranged in the X and Y directions are arranged on an outer peripheral portion of the stencil mask in a beam deflection range. Exposure method. 3. The transmission hole pattern formed by arranging a plurality of holes in the X and Y directions includes a striped pattern having a long side in the X direction and a rectangle having a long side in the Y direction. 3. The electron beam exposure method according to claim 1, further comprising a stripe pattern. 4. The size of the stripe pattern is such that several tens or more of the rectangular transmission holes constituting the stripe pattern are included in the cross section of the incident beam. Electron beam exposure method.