JPS62249417A - Electron beam lithography equipment - Google Patents

Abstract

PURPOSE:To render pattern dimensions more accurate by equipping an electron beam lithography equipment with a pattern data controlling circuit and making the circuit operate in accordance with a variation of dimensions of the electron beam, thereby composing the equipment so that an effective focal distance for the electron beam is variable and controllable. CONSTITUTION:A pattern data controlling circuit 2 controls a beam dimension controlling circuit 4 according to pattern information delivered by a CPU 1 and then sets electron beams injected by an electron gun 11 to have optimum beam dimensions by controlling beam formation diaphragms 12 and 13. At the same time, the CPU 1 calculates fluctuation of the focal position and controls a focal correction/control circuit 5. Thus, the circuit 5 performs a corrective control of the focal point of an objective lens 14 and permits the electron beam to carry out an image formation always at an overfocused position irrespective of variation of dimensions of the electron beam. After that, deflecting electrodes 15 and 16 scan the electron beam in directions of a plane X Y to draw a required pattern. Thus an effective focal length of the electron beam is kept constant, making it possible to perform the lithography under a condition of the highest accuracy of pattern dimensions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron beam lithography system used for microfabrication of patterns, and particularly to an electron beam lithography system designed to improve pattern accuracy.

[Conventional technology]

In the manufacturing process of semiconductor devices, resists and Sogerafuie processes are used relatively often, but in recent years -
With the miniaturization of device patterns, lithography systems that use electron beams are being used to pattern resists. This electron drawing apparatus performs pattern exposure by forming an image of an electron beam set to a required beam size (area) on a resist, and irradiating the resist with the electron beam following a required pattern.

Conventionally, this type of electron beam lithography equipment was developed in Japanese Patent Application No. 59-199
As described in No. 553, the objective lens is set so that the beam state is overfocused at the electron beam irradiation point. In other words, in a normal electron beam lithography system, since there is a relationship between pattern dimensional accuracy and effective focal length change as shown in Figure 3, it is possible to create a high pattern by slightly overfocusing the beam from the just focus point. Dimensional accuracy can be obtained.

[Problem that the invention seeks to solve]

As a result of various studies conducted by the present inventor regarding this type of device, the following was found: As shown in FIG. 4, when the beam size (area) of the electron beam changes, Since the number of electrons in the beam is increased or decreased, the mutual repulsion force (Coulomb repulsion) between electrons in the electron beam changes as the number of electrons changes, and the effective focal length also changes accordingly.

Therefore, if the beam dimensions are changed according to the pattern dimensions during electron beam exposure, the effective focal length will change accordingly, making it difficult to maintain high and stable dimensional accuracy of the exposed pattern. This results in a decrease in the reliability of the lithography process.

An object of the present invention is to provide an electron beam lithography apparatus that always focuses an electron beam on a predetermined focal position regardless of differences in electron beam area, thereby making it possible to perform exposure with high pattern dimensional accuracy.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the electron beam drawing apparatus is provided with a pattern data control circuit, and this control circuit is configured to operate in response to changes in the area of the electron beam to control changes in the effective focal length of the electron beam.

[Effect]

According to the above-mentioned means, the effective focal length of the lens for the electron beam is changed in accordance with the change in the area of the electron beam, and thereby the electron beam is always focused on a predetermined position to ensure high pattern dimensional accuracy. Can be done.

[Embodiment 1] FIG. 1 is a block diagram of an embodiment of the present invention, in which 10 is a lens barrel section of an electron beam lithography apparatus, and an electron gun 11. Beam shaping aperture 12, 13. Objective lens 14 and deflection electrode 1
5.16. Then, the electron beam emitted from the electron gun 11 is set to a predetermined beam area by the beam shaping aperture 12.13, and then the object is imaged and irradiated with the electron beam by the objective lens 14. In addition, the electron beam is directed to the plane X by deflection electrodes 15 and 16 connected to a scanning control circuit (not shown)
Scan in the Y direction to expose a desired pattern.

The lens barrel section 10 is provided with a CPUI, to which is connected a pattern data control circuit 2 that outputs beam dimensions and other conditions corresponding to the pattern to be drawn.

An electron gun control circuit 3 is connected to this, and the pattern data control circuit 2 controls the emission of the electron beam in the electron gun 11. A beam size control circuit 4 is also connected to this via amplifiers 4a and 4b. The beam shaping apertures 12 and 13 are controlled.

A focus correction/control circuit 5 is connected to the cput, which is connected to the objective lens 14 via an amplifier 5a to change and control its focus.

According to this configuration, the pattern data control circuit 2 has CP
Pattern information output from the UI! (shot size information) to control the beam size control circuit 4 and further control the beam shaping aperture 12.
The electron beam emitted from 1 is set to the optimal beam area for drawing the pattern.

At the same time, the CPUI calculates the focal position fluctuation due to the beam area, and controls the focal point correction/control circuit 5 based on this. As a result, the focus correction/control circuit 5 corrects and controls the focus of the objective lens 14 to always image the electron beam at a predetermined position, here an overfocus position, regardless of changes in the beam size of the electron beam. Then the deflection electrode 15.1
6, a desired pattern is drawn by scanning the electron beam in the XY direction of the plane. This makes it possible to keep the effective focal length of the electron beam constant and perform drawing with the highest pattern dimensional accuracy.

[Embodiment 2] FIG. 2 is a diagram showing another embodiment of the present invention, and the same parts as in FIG. In this embodiment, a shot current calculation circuit 6 is inserted between the pattern data control circuit 2 and the electron gun control circuit 3, and the electron gun 1
The structure is such that the electron beam current density in No. 1 can be varied and controlled according to the pattern.

According to this configuration, by changing the current density of the electron beam, the Coulomb repulsion in the electron beam is changed, and instead of controlling the focus of the objective lens 14, the effective focal length of the electron beam in the objective lens 14 is changed. Can be done. Therefore, by controlling the electron beam current density from the electron gun 11 in the shot current calculation circuit 6,
The effective focal length can be kept constant corresponding to each electron beam area, and pattern dimensional accuracy can be made high.

According to the embodiment described above, the following effects can be obtained.

(1) Since the effective focal length of the objective lens is controlled to change according to the area of the electron beam, changes in the imaging position caused by Coulomb repulsion are prevented and the electron beam is always focused at a constant position. It is possible to perform electronic drawing with high pattern dimensional accuracy.

(2) Since the focal length of the objective lens is controlled according to the pattern data of the electron beam, the focus can be automatically set optimally according to the area of the electron beam.

(3) By controlling the electron beam current, the focal length can be substantially controlled, and the focal length can be controlled without complicating the correction/control circuit in the objective lens.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, a correction lens may be attached to the objective lens, an electrostatic lens using an electric field may be used as the correction lens, and the focal length of the electron beam may be corrected based on the strength of the electric field. Similarly, an electromagnetic lens that utilizes a magnetic field may be used as the correction lens, and the focal length of the electron beam may be corrected based on the strength of the magnetic field.

In addition, when controlling the focus, the electron beam area.

The beam current density may be divided into a plurality of ranges, and the focus correction may be performed for each division unit. Furthermore, in this case, focus correction may be performed for each shot.

In the above explanation, the invention made by the present inventor has been mainly applied to a drawing device for element patterns in a semiconductor device, which is the background field of application. It can be applied to a device for drawing patterns in

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

In other words, the electron beam lithography system is provided with a pattern data control circuit, and this control circuit is configured to operate in response to changes in the area of the electron beam to control changes in the effective focal length of the electron beam. By changing the effective focal length of the lens for the electron beam according to changes in the beam area, it is possible to always focus the electron beam on a predetermined position and ensure high pattern dimensional accuracy, making it possible to draw fine patterns. and its formation can be achieved.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram of another embodiment of the invention, and FIG. 3 is a diagram showing the relationship between pattern dimensional accuracy and effective focal length change. FIG. 4 is a diagram showing the relationship between focal length and electron beam area. 1...CPU, 2...Pattern data control circuit, 3
...electron gun control circuit, 4...beam size control circuit,
5... Focus correction/control circuit, 6... Shot current calculation circuit, 10... Lens barrel section, 11... Electron gun, 12.
13...Beam shaping diaphragm (Figure 2) n (Figure 3) (Figure 4)

Claims (1)

[Scope of Claims] 1. In an apparatus for drawing a desired pattern by irradiating an electron beam, a pattern data control circuit is provided as part of a circuit for controlling a lens barrel section of the electron beam drawing apparatus, and the control circuit 1. An electron beam lithography apparatus characterized in that the electron beam lithography apparatus is configured to be operated in response to changes in the area of the electron beam to control changes in the effective focal length of the electron beam. 2. The electron beam lithography apparatus according to claim 1, wherein the pattern data control circuit is configured to correct and control the focal length of the objective lens provided in the lens barrel. 3. The electron beam drawing apparatus according to claim 1, wherein the pattern data control circuit is configured to control an electron gun provided in the lens barrel to control the electron beam current.