JPS6276619A - Multicharged beam lighography equipment - Google Patents

Abstract

PURPOSE:To improve the image drawing speed and image drawing accuracy by a method wherein a screen lens plate constituting a matrix lens is bent in a specified direction so as to compensate the bending of an image plane on a small lens group and to prevent the image being out of focus due to the bending of the image plane of a small lens group constituting the matrix lens. CONSTITUTION:A screen plate 19 is formed being bent so that the side of a wafer 21 is dented. The object point distance of each small lens group 20 in the matrix lens when an object apature 16a is assumed to be the object point is longer at a circumferential small lens and smaller at a central small lens. There is a tendency that the image point of an electron beam passing through small lens 20b and 20c is shorter than that passing through the central small lens group 20a due to the image bending. Therefore, it is possible to securely focus the electron beam passing through all the small lens groups 20 on the wafer by adjusting the degree of the benging of the screen lens plate 19.

Description

[Detailed description of the invention] [Technical field of invention] TECHNICAL FIELD The present invention relates to an improvement in a multi-charged beam writing apparatus.

[Technical background of the invention and its problems]

In recent years, integrated circuits have become more and more densely packed, and for this reason, electron beam lithography systems, which are relatively easy to form fine patterns, have come to be used for pattern formation. However, the number of wafers that can be processed per unit time by electron beam writing is still small, and at present it has not been widely used in integrated circuit manufacturing. ' Therefore, in order to shorten the drawing time, a so-called multi-beam drawing apparatus using a plurality of electron beams has recently been developed. FIG. 3 is a schematic configuration diagram showing a conventional multi-electron beam drawing apparatus, in which 30 is an electron gun, 34 is a focusing lens 34, 35 is a blanking plate, 36 is an objective aperture mask having an aperture 36a, 37. 38
39 is an electrostatic deflector, 39 is a screen lens plate, 40 is a small lens group, 41 is a wafer, and 42 is a sample stage.

In this apparatus, the electron beam is deflected so as to move the apparent upper position of the objective aperture 36a while keeping the irradiation position on the screen lens plate 39 unchanged. The same pattern is drawn at the same time.

Note that the screen lens plate 39 has one chip per chip.
A large number of small lens groups 4 so that one lens is assigned
0 are arranged in a matrix, and the small lens group 4o
The electron beam that has passed through is focused by an impregnated lens formed by an accelerating electric field between the screen lens plate 39 and the wafer 41, and is focused on the wafer 41 under each small lens group 40 by the reduction of the objective aperture 36a. Tie the statue.

When the deflectors 37, 38 are operated, these reduction ridges move by the same amount under each lenslet. Therefore, by moving the sample stage 42 in synchronization with the deflection of the electron beam, one chip can be drawn. Here, 1
Each electron beam passing through two small lenses writes one chip at the same time, so when one chip is finished writing, the number of chips equal to the number of small lens groups has been written, and as a result, the overall drawing Speed can be increased.

However, this type of drawing device has the following problems. In other words, the larger the number of small lenses, the more chips can be drawn at the same time, and the drawing speed can be increased accordingly. However, due to the curvature of field of each lens, it is necessary to arrange them in a 7-trix pattern as shown in Figure 4. The focal position of the beam differs between the small lens 40a at the center of the small lens group and the small lenses 40b and 40c at the periphery. If the electron beam passing through the central small lens 40a is focused on the wafer 41, the electron beam passing through the peripheral small lenses 40b and 40G will be focused in front of the wafer 41; A blur of the elephant appears in some areas. Since the blur caused by this field curvature increases as the distance from the objective aperture axis increases, it limits the number of small lenses, that is, the number of chips that can be drawn at the same time.

The above-mentioned problem is not limited to electron beam lithography, but also applies to ion beam lithography apparatuses that draw patterns using ion beams.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to prevent blur caused by field curvature of the small lens groups constituting the matrix lens;
An object of the present invention is to provide a multi-charged beam drawing device that can improve drawing speed and drawing accuracy.

[Summary of the invention]

The gist of the present invention is to correct the field curvature of the small lens group by curving a screen lens plate forming a matrix lens in a predetermined direction.

That is, the present invention provides a multi-charged beam writing apparatus that focuses a charged beam onto a sample using a group of small lenses arranged in a matrix on a screen lens plate, and simultaneously draws the same pattern at a plurality of locations on the sample. The screen lens plate is curved to have a concave surface toward the sample side.

〔Effect of the invention〕

According to the present invention, the image point distance of the small lenses on the periphery of the matrix lens is shorter than the image point distance of the small lenses in the center, and as a result, the field curvature of the small lens group is corrected. Therefore, even if the number of small lenses is increased to increase the number of chips that can be drawn at one time, there is no problem such as blurring at the periphery of the sample. Therefore, faster and more accurate drawing becomes possible, which is extremely effective in manufacturing integrated circuits.

[Embodiments of the invention]

Hereinafter, the measurement of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing a multi-charged beam lithography apparatus according to an embodiment of the present invention. 10 in the figure is an electron gun, and this electron gun 10 is formed from a cathode 11, a grid 12, and an anode 13. The electron beam emitted from the electron gun 10 is focused by a focusing lens 14,
The objective aperture mask 16 is uniformly illuminated. lens 1
4 and the aperture mask 16 is a blanking plate 1.
5 is arranged, and this blanking plate 15 turns the beam ON and OFF according to drawing pattern information. The electron beam that has passed through the aperture 16a of the objective aperture mask 16 is irradiated onto the entire screen lens plate 19. In other words, the electron beam passing through the objective aperture 16a passes through the objective aperture mask 16 and the screen lens plate 1.
9 and a number of beam-limiting apertures and lens apertures (not shown) on either side of the divergent drift space between the
The entire screen lens plate 19 having the following illumination is illuminated. In the drift space, 2 gA electrostatic deflectors 17 and 18 are arranged spaced apart in the optical axis direction.

These deflectors 17, 18 are connected to the screen lens plate 19.
The electron beam is deflected so that the apparent upper position of the objective aperture 16a moves while keeping the upper irradiation position unchanged. That is, by returning the electron beam that has been internalized by the upper deflector 17 by one angle by the lower deflector 18, the position of the objective aperture 16a as seen from the screen lens plate 19 is kept unchanged. Then, the electron beam that passed through the screen lens plate 19 is
The wafer 21 placed on the sample stage 22 is irradiated and imaged.

The i-line configuration up to this point is the same as that of the conventional device, and the present device differs from this in that the screen lens plate 19 is curved. That is, the screen plate 19 is curved so that the objective aperture mask 16 side is convex and the wafer 21 side is concave. Note that the degree of this curvature may be determined based on various conditions as described later.

When the screen lens plate 19 is curved as described above,
When the objective aperture 16a is taken as the object point, the object point distance of each small lens group 20 of the matrix lens is long for the peripheral small lenses and short for the central small lens. As a result, 12
As shown in the figure (when the electron beam passing through the central small lens 20a is focused on the wafer 21, the ideal imaging plane (Gaussian plane) is also shown by the curve 26 in the figure, and the objective aperture However, as mentioned earlier, the electron beam passing through the small lenses 20b and 20c on the periphery is curved in the image, compared to the electron beam passing through the small lens 20a in the center. There is a property that the distance between the electron beams becomes curved.Therefore, by optimizing the degree of curvature of the screen lens plate 19, it is possible to reliably focus the electron beams that have passed through all the small lens groups 20 onto the wafer 21. .

The curved shape of the screen lens plate 19 is determined by the image curvature of each small lens group 20 forming the 7-trix lens, and depends on the distance between the objective aperture mask 16 and the screen lens plate 19, the diameter of the small lenses, and the diameter of each small lens. It is determined by experiment or calculation from the angle of incidence of the electron beam on the lens, the potential between the objective aperture mask 16 and the screen lens plate 19, and the like.

In this way, according to this embodiment, the screen lens plate 19
By having a curved structure, it is possible to prevent the occurrence of blur caused by image curvature of the small lens group 20 constituting the matrix lens, and it is possible to perform highly accurate drawing.

Furthermore, since the blurring described above is eliminated, the number of small lens groups 20 can be increased, thereby improving the overall drawing speed. Another advantage is that there is no need to add any special parts to the conventional device, and it can be realized with a simple configuration by simply changing the shape of the screen lens plate.

It should be noted that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist and gist thereof. For example, the configuration of the optical system closer to the electron gun than the screen lens plate is not limited to that shown in FIG. 1;

It can be changed as appropriate by combining an aperture mask, a deflector, etc. Furthermore, the present invention can be applied not only to electron beam lithography but also to ion beam lithography.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a multi-electron beam lithography device according to an embodiment of the present invention, FIG. 2 is a schematic diagram for explaining the operation of the device, and FIG. 3 is a schematic diagram showing a conventional device. , FIG. 4 is a schematic diagram for explaining the problems of the above-mentioned conventional device. DESCRIPTION OF SYMBOLS 10... Electron gun, 11... Cathode, 12... Grid, 13... Anode, 14... Focusing lens,
15... Blanking plate, 16... Objective aperture mask, 16a... Aperture, 17.18... Electrostatic deflector, 19°... Screen lens plate, 20...
Small lens group, 20a, 20b, 20c... small lens,
21--Wafer (sample), 22--Sample stage. Applicant's representative Patent attorney Takehiko Suzue? 'ij I Prisoner Figure 2

Claims (2)

[Claims] (1) A charged beam is focused onto the sample by a group of small lenses arranged in a matrix on a screen lens plate,
A multi-charged beam drawing device for drawing a predetermined pattern on the sample, characterized in that the screen lens plate is curved to form a concave surface toward the sample. (2) The degree of curvature of the screen lens plate is set so that the beam passing through the central small lens of the small lens group and the beam passing through the peripheral small lenses are converged on the same plane. 2. A multi-charged beam lithography apparatus according to claim 1, wherein the multi-charged beam lithography apparatus is