JPS6253939B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an electron beam lithography apparatus.

Conventionally, in order to form fine patterns, an electron-sensitive resin thin film whose properties can be changed by electron beams is formed on the workpiece (this is called an electron beam resist), and a finely focused electron beam is applied to this thin film. What is being done is drawing a pattern. In this case, in order to draw fine patterns with high precision, a computer controls the beam position and the interruption of the electron beam. This device is generally called an electron beam lithography (or exposure) device.

In conventional writing apparatuses, only beam on (ON) and off (OFF) control was performed in order to keep the electron beam scanning speed constant and obtain a desired pattern. Normally, an electron beam incident on one point has an exposure intensity distribution as shown in FIG. 3a, and the electron beam exposure extends to the periphery. This phenomenon is caused by energy loss caused by inelastic collisions when electrons pass through the electron beam resist, and the sensitive region of the electron beam resist is caused by scattering of the primary electron beam and backscatter from the substrate. is determined by the sum of the areas of and its strength. This exposure intensity distribution differs depending on the electron energy, the material of the substrate, etc.

On the other hand, if we look at this distribution in the opposite way, we can see that the irradiation point P
When an electron enters a point (X, Y) that is further away,
An exposure amount of F (x, y, X, Y) is added to point P. That is, it can be seen that the exposure amount at point P changes depending on whether or not electrons are incident within the influence range based on the distribution.

That is, the exposure amount E(x,y) at any point is expressed by equation (1).

E(x,y)=∫∫N(X,Y)F(x,y,
X, Y) dX, dY (1X-x1, 1Y-y1ε) (1) where N(X, Y) is a function or data of the normalized dose, and ε is an arbitrary point given empirically. It is an integral range centered on (x, y), and it is usually sufficient to take around 4 μm.

In conventional equipment, if a pattern exists, N
(X, Y)=1. However, if there is no N
(X, Y)=0. Therefore, as shown in FIG. 3b, when drawing a large rectangle with a uniform dose, the position where the exposure dose is maximum is at the center of gravity of the pattern, and the position where it is minimum is at the four corners. The numbers shown in the figure indicate relative exposure amounts with the maximum exposure amount being 1.

In the exposure process, the exposure amount E(x,y) is
As shown in equation (2), the size of the figure to be drawn is determined so that it is larger than the critical sensitive electron quantity E _S of the electron beam resist in the drawing area and smaller than the critical electron quantity E S in the other areas.

Ed (x, y) E _S (drawing position) (2) Eb (x, y) < E _S (non-drawing position) In the case of Figure 3b, the exposure amount at the four corners is 1/4 compared to the center of gravity. , Equation (2) shows that the corners of the rectangle are rounded. This is the proximity effect. Furthermore, due to the adjacency of figures, a highly accurate pattern cannot be obtained even though the electron beam diameter is extremely small.

Therefore, in order to obtain a fine pattern or a highly accurate rectangular pattern, it is necessary to obtain a drawing method and a drawing apparatus that take the above-mentioned proximity effect into consideration.

The purpose of the present invention has been made with attention to the above points, and is to deal with the proximity effect that occurs when drawing fine patterns using electron beams.
The object of the present invention is to obtain a device that can draw fine and precise patterns.

In order to achieve the above object, the present invention newly provides a function to give weight to the irradiation amount in the electron beam drawing area. N(X, Y) in equation (1) is calculated backwards in advance to obtain the desired pattern under the conditions of equation (2), and based on this relationship, the electron beam is pulse width modulated to expose the desired pattern position. Turn on the electron beam by taking the product with the blanking signal (blanking signal).
This method uses a method of controlling the electron beam exposure amount by performing OFF modulation.

Hereinafter, the present invention will be explained in detail with reference to Examples. FIG. 1 is a block diagram showing one embodiment of the present invention. Further, FIG. 2 shows waveforms at various parts of the present invention.

In FIG. 1, the dose control is performed by the dose signal output from the dose control signal generation circuit 9 (see FIG. 2a).
) and a sawtooth wave (FIG. 2b) as a reference voltage of the comparator circuit 8 are inputted from the reference voltage generator 12 to the comparator circuit 8 to perform pulse width modulation.
Furthermore, the signal obtained from the electron beam intermittent signal generator 13 (FIG. 2 d) for specifying a desired pattern position is input to the multiplication circuit 7, and this signal and the above modulation signal (FIG. 2 c) The product is calculated and shaped into a dose control signal (Fig. 2e) that can be used for drawing. This control signal is input to a conventionally used blanking circuit 6, and the electron beam 2 emitted from the cathode 1 is turned on and off by a blanking plate 5. In addition, in the figure, 3 indicates a sample to be processed, and 4 indicates a sample moving table.

The dose control signal generation circuit 9 calculates in advance the dose N(X, Y) of equation (1) that satisfies the condition of equation (2) so that the desired pattern can be obtained, and the dose N(X, Y) of equation (1) is calculated in advance from the computer 11 to the interface 10. programmed via. Note that the lines to be programmed are omitted in FIG.

As explained above, the irradiation dose signal N(X, Y) is subjected to pulse width modulation by the reference voltage generating section 12 and the comparator circuit 8. After multiplication with the blanking signal, beam blanking can be performed and proximity effect correction can be performed.

A specific example of the proximity effect correction will be explained using the case shown in FIG. 3b.

In order to correct this proximity effect, the amount of exposure may be corrected so that the amount of exposure within the figure is uniform. Third
Figure c is an example in which the dose within the rectangle is corrected based on Figure 3b. In the case of the B scan shown in FIG. 3b, if the relative irradiation amount at the corner portions is 1, it is necessary to reduce the relative irradiation amount to 1/2 at the center portion. In addition, in the case of A-scanning, it is necessary to start with 1/2 irradiation dose and correct it to 1/4 irradiation dose in the central area.

Such a function or data of the exposure dose must be calculated backward from the distribution of the figure and the exposure intensity distribution. The exposure intensity distribution in this case can be determined experimentally. This distribution function has no meaning unless it is determined experimentally, as it is influenced by the various conditions mentioned above. Therefore, the dose N(X, Y) in FIG. 3c is greatly influenced by the above distribution function, and is preferably processed by computer using advanced numerical analysis methods. Incidentally, FIG. 3c is a specific example of the signal shown in FIG. 2a. Instead of making the irradiation amount within the rectangle more uniform, N(X, Y) may be created so as to satisfy the condition such as equation (2). This N
By inputting (X, Y) into the comparison circuit 8 and performing pulse width modulation as described above, proximity effect correction is realized.

On the other hand, the repetition frequency of the sawtooth wave in the electron beam intermittent signal generating section 13 depends on the electron beam scanning speed, but must be set so that the repetition period is equivalent to 0.1 μm or less.

As explained above, according to the present invention, a designed drawing pattern can be drawn without the pattern being disturbed by the proximity effect, with a fine size figure and a fine pattern having a minute interval between figures. It can be obtained by subsequent development. Further, according to the present invention, it is possible not only to control the exposure amount for each rectangular pattern, but also to control the exposure amount within a rectangle.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining an embodiment of the present invention, FIG. 2 is a time chart for explaining the present invention, and FIG. 3 is an explanatory diagram for explaining proximity effect correction. In the figure, 1 is a cathode, 2 is an electron beam, 5 is a blanking plate, 6 is a blanking circuit, 7 is a multiplication circuit, 8 is a comparison circuit, 9 is a dose control signal generation circuit, 10 is an interface, and 11 is a calculator, 1
2 is a reference voltage generating section, and 13 is an electron beam intermittent signal generating section.

Claims (1)

[Claims] 1. In an electron beam drawing device that draws a fine pattern on a workpiece using an electron beam,
Dose control circuit means for generating a weighted dose signal to control the electron beam exposure dose received from a nearby area during drawing, and pulse width modulation for pulse width modulating the signal output from the dose control circuit means. means for generating an intermittent electron beam signal for exposing at a desired pattern position; multiplication circuit means for obtaining the product of the intermittent signal from the intermittent signal generating means and the modulation signal from the pulse width modulating means; and the multiplier. It is characterized by comprising a blanking means for turning on and off the electron beam based on a signal generated from the circuit means, and configured to be able to control the irradiation amount of the main electron beam in order to correct the proximity effect of the pattern to be drawn. Electron beam lithography equipment.