JPS6250975B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam exposure apparatus, and more particularly to an electron beam exposure apparatus that can draw fine patterns of integrated circuits on masks, wafers, etc. with high precision.

As the pattern dimensions of integrated circuits tend to become smaller year by year, it is becoming difficult to manufacture them using mask manufacturing methods that rely on conventional optical exposure technology.
For this reason, an electron beam exposure technique that performs exposure using an electron beam has become indispensable in place of the optical exposure technique.

The mask manufacturing and wafer manufacturing process using electron beam exposure technology will be explained as follows.
Prior to exposure, a material to be etched during exposure, usually an oxide film or a metal film, is formed on a mask or a wafer substrate, and a workpiece material is prepared with a resist film coated on this material. I'll keep it. This material to be processed is placed on a sample stage provided in a mirror body of an electron beam exposure device, and the beam is moved to a portion corresponding to a pattern under the control of an electronic computer, and irradiates the material to be processed. The irradiated areas undergo a polymerization reaction with the resist, and if the resist material is positive, it becomes soluble in the developer, and if it is a negative resist, it becomes insoluble. The soluble region becomes a window in the next etching process and a pattern in the diffusion process or wiring process.

In this manner, when exposure is performed using an electron beam, whether or not the resist remains is determined depending on the amount of the irradiated electron beam. Even if the diameter of the electron beam is narrowed down, it is thought that charges will accumulate around the irradiated position according to a Gaussian distribution function.

For this reason, one of the conditions for writing on a mask or wafer is that when multiple patterns are placed close to each other, direct irradiation with an electron beam occurs due to the superposition effect of the amount of charge accumulated in those patterns. When the resist becomes soluble to the extent that it is not soluble, the desired pattern cannot be obtained, and the pattern is distorted (this is called the proximity effect)
There is.

What influences the amount of charge in an electron beam exposure apparatus is the irradiation current value of the electron beam and the clock frequency that determines the beam movement speed. The relationship between current value, clock frequency, and amount of accumulated charge is given by the following equation.

S (c/cm ² )=(I/kf)×10 ⁸ Here, S is the accumulated charge per unit area, I is the irradiation current value, f is the clock frequency, and k is a constant.

In conventional electron beam exposure equipment, a pattern is usually drawn by setting the current value and clock frequency in accordance with the sensitivity of the resist. However, the drooping of the pattern edges and the pattern spreading effect caused by the above-mentioned superposition effect are fatal defects when manufacturing a large-scale integrated circuit that requires a pattern with a line width of 1 μm.

Hereinafter, the above-mentioned problems will be explained in more detail with reference to the drawings.

FIG. 1 shows the distribution of the amount of charge accumulated in the resist when the beam is irradiated onto the material to be processed. As shown in the figure, when the beam is irradiated to the central position, the charge accumulation distribution state becomes a Gaussian distribution 11. Whether a pattern is etched or not depends on the amount of accumulated charge per unit area. Regarding Figure 1, Q in the figure
The portion of the region P1 where the charge has been accumulated is removed by etching, that is, it is removed.

FIG. 2 is a diagram showing pattern distortion when patterns are close to each other. When the accumulated charge distributions 12 and 13 of the two figures P2 and P3 are close to each other, a charge superimposition effect occurs between the patterns, and a portion having a charge of Q or more exists. In such a case, as shown in the figure, patterns P2 and P3 are combined into one pattern, which has no meaning as a diffusion layer pattern or wiring pattern in an integrated circuit.

The purpose of the invention is to be able to avoid superimposition effects and thus:
An object of the present invention is to provide an electron beam exposure device capable of drawing fine patterns.

The electron beam exposure apparatus of the present invention includes a memory section that stores information on a pattern to be drawn as blanking information that determines whether the beam is turned on or off for each beam irradiation position, and blanking information for each irradiation position and the blanking information for each beam irradiation position. The apparatus is characterized in that it includes a mechanism for varying the clock frequency by referring to blanking information in the vicinity of the irradiation position.

More specifically, in the blanking information stored in the memory section, the on/off state of the beam for each irradiation position (address point) is expressed by a "1" or "0" bit. Electron beam control is performed for each address point. however,
When the beam is irradiated in a close area, charge is accumulated in areas other than the irradiation point as described above. Therefore, in the present invention, such a situation is assumed in advance, and the beam irradiates in the area described above. Reduce the amount of radiation.

In order to achieve the above object, in the present invention, blanking data of a position to be irradiated and blanking data of address points near the position are stored in a group of registers, and the contents of these registers are transferred to a comparator. The beam scanning clock frequency is changed depending on the comparison result, and the amount of accumulated charge is substantially changed depending on the position of the beam.

The degree to which the clock frequency should be changed depends on the type of resist applied to the workpiece material, but if the amount of scattering of the irradiation beam within the resist is large, the effect near the irradiation position will be large. Therefore, it is desirable to increase the speed of the irradiation beam. Since the charge distribution state is generally represented by a Gaussian distribution, it is necessary to provide a frequency dividing circuit with a mechanism that allows the clock frequency to be changed continuously.

When comparing, how far away from the beam position should the data of the address point be compared?
Depending on the resist of the material to be processed and the required resolution of the pattern, the apparatus of the present invention can change these ranges by setting external parameters.

Next, the conventional electron beam exposure apparatus (FIG. 8) will be described in more detail with reference to FIGS. 3, 5, and 8.

First, referring to FIG. 8, a conventional electron beam exposure apparatus includes a processing device 1, and this processing device 1 is provided with a charged particle generation source 2 that generates an electron beam. An electron beam generated from a charged particle generation source 2 is focused by a focusing lens 3 and irradiated onto a workpiece material 5 . In this case, the irradiation position is controlled by the deflection device 4, and the beam is turned on and
Off is controlled by a blanking device 6.

A blanking signal is given to the blanking device 6 through a blanking register 7, while a signal to the deflection device 4 is given to each register giving the position in the X and Y directions and the deflection speed, namely an X register 8 and a Y register. 9, supplied from the F register 10.

Furthermore, all data transfers to these registers are controlled by the control system 11. in this case,
A constant value determined by the sensitivity of the resist is given to the F register 10, and the electron beam moves at a constant clock frequency corresponding to this value. The illustrated control system 11 is provided with a memory (not shown) that stores only the end point information of the figure as an interface with each register 8-9, and this end point information is sequentially stored in the registers 8 and 9. sent to.

Referring to FIG. 3, the relationship between a plurality of patterns exposed by the conventional electron beam exposure apparatus shown in FIG. 8 and the scanning speed of the beam at the address point within each pattern is shown. . As indicated by I in the figure, the scanning speed of the beam at each address point is constant.

Referring to FIG. 5, a pattern exposed and etched by the exposure apparatus shown in FIGS. 8 and 3 is shown. As is clear from FIG. 5, portions of each pattern adjacent to other patterns are distorted due to the above-mentioned superimposition effect.

An electron beam exposure apparatus according to an embodiment of the present invention will be described with reference to FIGS. 4, 6, 7, and 9. As shown in FIG. 9, the electron beam exposure apparatus according to the present invention uses a seventh
It has a memory section that stores pattern information as shown in the figure. To clarify the differences in the information stored in the memory sections, the memory sections in FIG. 9 are designated by the reference numeral 14.

In FIG. 7, positions that require beam irradiation are represented by logic "1", while positions that do not require beam irradiation are represented by logic "0". In this figure, the positions in the x and y directions are represented as x _i and y _i , respectively, and the information stored at the positions in the x and y directions, that is, blanking information Px _i , y _i
It is expressed as

Returning to FIG. 9, the memory section 14 stores x and y.
Position information x _i , y _i in the direction is stored, and each position information x _i , y _i is sequentially read out under the control of the control system 11 and stored in the X and Y registers 8 and 9. This position information indicates the position of the beam to be exposed.

On the other hand, blanking information Px _i , y _i that determines whether the beam is turned on or off is read from the address of the memory unit 14 specified by the position information x _i , y _i ,
It is stored in the blanking register 7. In this state, under the control of the counter circuit 15,
The positional information in the direction is counted up and down by a predetermined number, and blanking information Px _i , y _i at each position is stored in the blanking register 16 .

Here, it is assumed that the positions x _i and y _i are specified as the irradiation beam positions by the position information. At this time, the blanking register 16 sequentially stores, as blanking information, blanking information of positions close to the positions x _i and y _i . For example, the seventh
Px _i+1 , y _j , Px _i+2 , y _j , Px _i-1 , y _j ,
Px _i-2 , y _j , Px _i , y _j+1 , Px _i , y _j+2 , Px _i , y _j-2
Blanking information such as the following is stored as blanking information at positions near the positions x _i and y _i .

On the other hand, blanking information Px _i and y _i at positions x i _and y _i are stored in the blanking register 7, as in the case of FIG.

In this state, the contents of both blanking registers 7 and 16 are compared by the comparator 12, and when the blanking information at the adjacent position is all "0", it is assumed that there is no influence from other patterns, and the fourth
The beam is irradiated at a standard scanning speed as shown by I in the figure. On the other hand, if the blanking information at the adjacent position is not all “0”, the position Px _i , y _i
Vary the scanning speed at .

FIG. 4 shows an example in which the scanning speed of each pattern at a position close to another pattern is changed from the standard scanning speed I to I' and I''.

In this way, in order to change the scanning speed, the frequency dividing circuit 13 generates a frequency according to the strength of the influence from other patterns, that is, the magnitude of the output signal from the comparator 12. do. In this way, as shown in FIG. 4, scanning speeds I' and I'' different from the reference scanning speed can be obtained. As a result, a normal pattern can be obtained as shown in FIG. 6. .

According to the electron beam exposure apparatus of the present invention, since it has a function of determining the mutual situation of adjacent patterns and dynamically changing the beam irradiation speed,
Pattern distortion due to proximity effect can be prevented.

Therefore, even thin lines of 1 μm or less can be drawn with relative fidelity, making it possible to fully cope with the miniaturization of integrated circuit patterns. This not only helps dramatically improve the performance of integrated circuits, but also greatly contributes to improving reliability.

The electron beam exposure apparatus according to the present invention is not only useful for mask pattern drawing of integrated circuits and wafer direct exposure drawing, but also can of course be used for fine beam processing of printed boards.

The specific configuration of the present invention is not limited to the embodiments described above, and various other modifications are possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the distribution of accumulated charges in the workpiece material when the beam is irradiated, and FIG. 2 is a diagram showing the distribution of accumulated charges when there are adjacent patterns. Figure 3 is a diagram showing the scanning speed at each beam irradiation position of a conventional electron beam exposure system.
The figure is a diagram showing the scanning speed at each beam irradiation position based on the present invention. FIG. 5 shows a pattern drawn by a conventional electron beam exposure apparatus, and FIG. 6 shows an example of a pattern drawn by the present invention. 7th
The figure is a diagram illustrating the contents of a memory section in the configuration of the present invention. FIG. 8 shows an example of the configuration of a conventional electron beam exposure apparatus, and FIG. 9 shows an example of the configuration of an embodiment of the electron beam exposure apparatus according to the present invention. In the figure, 1... processing device, 2... charged particle generation source, 3... focusing lens, 4... deflection device, 5... material to be processed, 6... blanking device, 7... blanking register, 8... X register, 9...Y register, 10...F register, 11...control system, 12...comparator, 13...frequency divider circuit, 14...memory section,
15...counter circuit, 16...blanking register, 17...oscillator.

Claims (1)

[Claims] 1 has a memory section that stores charged beam deflection position information that specifies the irradiation position of the charged electric beam, and blanking information that determines whether the charged electric beam is turned on or off at each irradiation position; In this case, the deflection position information corresponding to the irradiation position is read from the memory section to the position register, while the blanking information at the irradiation position is read from the memory section to the first blanking register. A predetermined number of blanking information is stored in a second blanking register, the contents of the first and second blanking registers are compared by a comparator, and the clock frequency is continuously adjusted based on the comparison result. An electron beam exposure apparatus characterized in that a frequency dividing circuit that can be changed is controlled, and the moving speed of the charged beam is changed by the output of the frequency dividing circuit.