JPS609660B2 - Electron beam figure projection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention relates to an apparatus for irradiating a sample with a diagram-shaped electron beam, such as an electron beam lithography apparatus.

■ Substructure technology The method of irradiating an aperture plate with a graphic aperture with an electron beam and reducing and projecting the electron beam that has passed through the aperture plate using an electron lens is compared to the method of scanning a dotted electron beam in a figure shape. It has the advantage of being efficient because a large area can be formed at once.

Figure 1 shows the configuration of an electron optical system when implementing the former method, in which 1 is an electron source, 2 is a focusing lens, and 3 is an electron optical system.
4 is an electron beam diaphragm, 4 is an irradiation lens, 5 is a diaphragm plate (mask plate) having a graphic exit, 6 is a first projection lens, 7 is an electron beam diaphragm, 8 is a second projection lens, 9 is a work object, and At the same time, the distances between the mask plate 5 and the first projection lens 6 and between the first projection lens 6 and the electron beam diaphragm 7 are By configuring the distances between the electron beam diaphragm 7 and the second projection lens 8 and between the second projection lens and the working surface 9 to be equal to the focal length of the second projection lens, the focal length of both projection lenses can be made equal to the focal length of the second projection lens. Reduction is performed by ratio, and the aberrations of both projection lenses act complementary to each other to correct distortion.

FIG. 1a shows the configuration of the above optical system. Figure 1b
FIG. 1A is an explanatory diagram for adjusting the focus of the optical system shown in FIG. 1A. When focusing, first, the focal lengths of the focusing lens 2 and the irradiation lens 4 are changed to create a reduced image of the light source 1 on the mask plate 5. At the same time, the electron beam is deflected and scanned by a deflection element 101 placed at the front focal point of the irradiation lens 4. Then, reflected electrons and the like are detected on the work surface 9 and a scanned image is observed. At this time, the state in which both the images of the reference marks on the mask plate 5 and the work surface 9 are the clearest in the scanned image is the focused state. The problems with this configuration are as follows.

First, when transitioning from a focused state to a working state of the device, it is necessary to change the intensity of the irradiation lens 4, but in this case the irradiation lens 4 irradiates a wide area of the mask plate 5. Since a lens with a large diameter is used due to the need for projection, the lens action area of the irradiation lens 4 extends slightly below the mask plate 5, and the strength of the irradiation lens 4 can be changed below the mask plate 5, that is, in the direction of projection. It also changes the conditions and causes a shift in focus. Second, in the configuration shown in FIG. 1a, the electron beam passing through the periphery of the mask plate 5 cannot pass through the aperture 7 due to aberrations of the irradiation lens 4 and the first projection lens 6. If the aperture diameter of the diaphragm 7 is increased, this restriction will be relaxed, but in this case, the accuracy of the image will decrease due to a shift in focus due to the curvature of the image plane. Therefore, the area that can be projected at one time is limited. Further, in such a configuration, if the intensity of the electron beam irradiating the mask plate 5 is not uniform, it is impossible to correct it, and from this point as well, the area is limited. '3} Purpose of the Invention The main purpose of the present invention is to eliminate the above-mentioned drawbacks and to perform projection over a wide area while maintaining high accuracy.A further purpose is to make the irradiation density of the electron beam uniform. It is to make it.

'4} Example Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 2 shows the configuration of an embodiment of the present invention, and shows the state of projection, that is, the image of the light source 1 is projected by the focusing lens 2 at the front focal point of the irradiation lens 4, and at the same time by the deflection element. It is made at a position that is the deflection point of the electron beam.

In this case, the electron beam irradiating the mask plate is limited by the aperture 3 and is narrow. In this state, by scanning the electron beam over the entire surface of the mask plate using the deflection elements 10 and 10', a reduced image of the figure on the mask plate can be projected onto the work surface 9. However, when deflection is performed, the electron beam does not pass through the aperture 7 due to the aberration of the first projection lens.

That is, when the deflection angle is small as shown in FIG. 3a, the electron beam passes near the light beam and is almost affected by aberrations caused by the irradiation lens 4 and the first projection lens 6, as shown by the solid line. When the deflection angle is increased to pass the electron beam through the periphery of the mask plate, the focal length changes to become shorter due to the aberrations of the irradiation lens 4 and the first projection lens 6. As a result, as shown by the dotted line in FIG. 3a, the light deviates from the position of the aperture and cannot pass through. In order to prevent this, it is possible to change the position at which the electron beam is deflected downward, as shown by the solid line in FIG. 3b, so that the electron beam passes through the aperture. That is, as shown in FIG. 2, the deflection element is divided into upper and lower parts, and the upper deflection element 10 is mainly used in the range of small deflection angles.
When the deflection angle becomes large, if the deflection position is adjusted by increasing the proportion of the lower deflection element 10' and the structure is configured such that the electron beam can always pass through the aperture 7, it is possible to eliminate the limitations on the projection area due to aberrations. The diameter of the aperture 7 can be made sufficiently small. For this reason, it is possible to obtain a large depth of focus, and it is possible to keep the blur caused by the curvature of the bride surface sufficiently small, making it possible to project a large area with high accuracy. Furthermore, since the irradiation position is changed by scanning, the amount of the irradiated electron beam does not change.

However, if the deflection is large, lens aberration will cause the aperture to 7
The amount of electrons passing through varies. In this case, uniform exposure is possible by changing the scanning speed depending on the magnitude of deflection and correcting the electron beam density so that it is uniform on the work surface 9. As a correction method, in addition to the method of changing the scanning speed described above, the scanning interval may be changed. That is, correction can also be made by narrowing the scanning interval as the deflection angle increases and the amount of electrons passing through the aperture 7 decreases. Further, both of the above may be used in combination. However, in the case of the method of changing the scanning interval, since the correction is in one direction, after one scanning is completed,
By changing the scanning direction by 9 degrees and performing the same scanning again, correction in two directions, that is, two dimensions, can be performed. In addition, the focus adjustment has the same configuration as in FIG. 1b by making the focusing lens stronger and placing the light source 1 above the diaphragm 3.

In this case, there is no need to change the strength of the irradiation lens 4, so even if the device is switched from focus adjustment conditions to projection conditions, the conditions below the mask plate will not change at all, allowing accurate focus adjustment. Become. '5} Summary As explained above, according to the configuration of the present invention, accurate focus adjustment is possible without changing the conditions below the mask slope, and it is possible to adjust the focus without changing the movement of the deflection point and the scanning speed or scanning interval. This makes it possible to correct the projection area limitations and brightness caused by aberrations, while maintaining high accuracy.
Projection of a large area becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the configuration of a conventional projection device, FIG. 2 is a diagram illustrating the configuration of a projection device according to the present invention, and FIG. 3 is a diagram illustrating an example of the effects of the present invention. In the figure, 1...Light source, 2...Concentration lens, 3, 7...Aperture, 4...Irradiation lens, 5...
Aperture plate (mask plate), 6...first projection lens,
8...Second projection lens, 9...Work object,
10, 10'... Deflection element. Multi-figure. Tsutomu Ou's younger brother

Claims (1)

[Claims] 1. In an apparatus that uses an electron lens to reduce and project an electron beam that has passed through a mask having a figure-shaped aperture, the electron beam that irradiates the mask is limited to a small size, and the entire surface of the mask is irradiated with the electron beam by deflection scanning. An electron beam graphic projection apparatus characterized in that the effective deflection point in the deflection is changed according to the deflection angle.