JPS62285418A - Method of exposing pattern of minute width - Google Patents

Abstract

PURPOSE:To slide the central portion of a basic pattern at the time of the second exposure from the position of the central portion at the first time and thereby to give a final basic pattern substantially the same high precision with that of a designed pattern, by dividing an electron beam (EB) exposure into two steps and by reducing an amount of the first EB exposure. CONSTITUTION:The first of electron beam (EB) exposures of a designed pattern (a) based on a submicron pattern is conducted by means of a basic pattern (divided pattern). The second exposure is conducted at a position a 1/2 pitch off the one of the basic pattern at the first and the width of the pattern at that time is made slightly smaller than that at the first time. A nodal portion formed at a joint portion of each basic pattern at the first time is compensated with the central portion of the joint portion of each basic pattern at the second time, sinuosity and excessive thickness are thereby eliminated, and thus a final basic pattern is made substantially the same with the designed pattern.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Summary] When exposing a fine-width pattern with an electron beam shaped into a basic pattern of variable size, the fine-width pattern is exposed twice. At that time, the central part of each basic pattern when performing the second exposure is shifted to the joint part of each basic pattern when performing the first exposure. The pattern shape after exposure can be made into a highly accurate shape that is almost the same as the intended designed pattern.

[Industrial application field]

The present invention relates to an exposure method for fine-width patterns, and in particular, to a method for exposing submicron patterns for forming transistor gate 1a poles, etc. on a wafer using electron beam exposure (ILLI).
The present invention relates to an exposure method for forming fine-width patterns by conventional EB exposure.

[Prior Art] Conventionally, when forming submicron patterns such as transistor gate electrodes on a wafer, two slits having a predetermined maximum slit size are overlapped and their positions are adjusted to form a predetermined pattern. An electron beam formed into a basic pattern of a predetermined shape (for example, a rectangular shape) formed by a variable-sized aperture (an electron beam shaped into a predetermined beam size by a so-called variable rectangular beam forming method) ) are sequentially applied to the resist film on the wafer located below the slit to form a predetermined EB exposure pattern in the resist film, and then the EB exposed pattern portion is removed by development processing and metal is applied to that portion. By forming the layer, a gate electrode having a predetermined fine width pattern (for example, a submicron pattern) is formed and worn out.

FIG. 2 shows an example of an exposure method for such a fine-width pattern according to the prior art. For example, as shown in FIG. 2(b), the design pattern is divided into five basic patterns each having a width of 0.5 μm and a length of 1.0 μm, and EB exposure is performed for each of the divided basic patterns. , maximum slit size 1.0μm
Using two slits with a width of 1.0 μm (a square with a negative side of 1.0 μm), adjust their mutual positions to form an opening with a width of 0.5 μm and a length of 1.0 μm, which corresponds to the basic pattern. For example, the five basic pattern parts are sequentially inserted through the opening. OX 10-S coulomb/cn! The design pattern is exposed by sequential EB exposure using an electron beam having an exposure amount of .

[Problem that the invention seeks to solve]

However, when performing EB exposure on a fine width pattern such as a submicron line, the exposure dose must be increased compared to a normal pattern (for example, 3.OX 10-' coulombs/ cIll), therefore, by the conventional technology as mentioned above, EB
When exposure is performed, the pattern formed after exposure due to the spread of the electron beam during exposure is as shown in Figure 2(c).
As shown in , a joint appears at the seam of the divided rectangles (basic pattern) (in other words, both sides of the exposure pattern become waveform-like).
, resulting in a shape different from the intended linear design pattern as shown in FIG. 2(a).

Therefore, in order to improve the shape of the exposure pattern, as shown in Fig. 3, the size of the basic pattern for division is reduced (in the case of Fig. 3 (a), the maximum slit size is 0.5 μm x O , 5 μm, to form an opening with a width and length of 0.5 μm,
It is conceivable that 10 basic pattern parts are sequentially exposed to EB light through the aperture, but if the size of the basic pattern is reduced in this way, the exposure amount will increase unless the exposure amount for exposing the basic pattern is further increased. (In the case of Fig. 3, the exposure amount needs to be about 4.5 x 10-' coulombs/cffl, for example.) As a result, as the exposure time increases, the amount of light that is formed after the exposure increases. As shown in Fig. 3(b), the pattern shown in Fig. 3(b) becomes thicker on both sides of each basic pattern than in the case of Fig. 2(c) (although it becomes so-called fine waves and the undulation becomes smaller). (If you look at the overall average value, it will become even fatter)
As the deviation of the design patterns increases and the basic pattern for division is made smaller (by increasing the number of basic patterns for the same design pattern), the number of EB exposures also increases (for example, 10μ
m×10μm design pattern to 1.0μm×1.0μm
If you divide it using the basic pattern of 100 patterns,
There was a problem that 400 patterns were required if divided into basic patterns of 0.5 μm x 0.5 μm.

The present invention was made to solve this problem, and it is possible to reduce the exposure time without increasing the exposure time as a whole.
A desired pattern that substantially matches the design pattern can be formed as a pattern after B exposure.

[Means for solving problems]

In order to solve this problem, in the present invention, when exposing a fine-width pattern with an electron beam formed into a basic pattern of variable size, the fine-width pattern is exposed twice. , an exposure method for fine-width patterns, in which the center part of each basic pattern when the second exposure is performed is shifted to the joint part of each basic pattern when the first exposure is performed. is provided.

[For production]

According to the above configuration, by performing the two exposures, one
The amount of EB exposure for each exposure can be reduced, and in addition, at the second exposure, the center of each basic pattern is shifted so that it is located at the joint part of each basic pattern at the first exposure. Therefore, the joint portion formed at the joint portion of each basic pattern during the first exposure is compensated for by the central portion of each basic pattern during the second exposure, and the final portion after the second exposure is There is almost no undulation or thickening in the exposure pattern as in the above-mentioned prior art.

〔Example〕

FIG. 1 shows an EBi optical method as an embodiment of the present invention, and its features are, for example, as shown in FIG.
) When performing EB exposure of a design pattern consisting of a submicron pattern with a width of 0.5 μm, as shown in Fig. 1(b)
1 by the basic pattern (division pattern) shown in
The second EB exposure is performed on the main pattern (the center part is shown in Figure 1).
b) located at the joint part of the basic pattern),
EB exposure is performed again (therefore, the exposure amount for each basic pattern is smaller than that of the conventional example, for example, 2.0×10-'coulombs/cn!)
At the point.

In other words, during the first exposure, the design pattern is
Width 0.5μm, length 1.0μm as shown in figure (b)
m basic patterns, and for each divided basic pattern, for example, the above 2. OX 10-5 coulombs/cJ
EB exposure is performed with an exposure amount of . In other words, by adjusting the mutual position of two slits having a maximum slit size of 1.0 μm x 1.0 μm, an opening with a width of 0.5 μm and a length of 1.0 μm corresponding to the basic pattern is formed. , the basic pattern is sequentially subjected to EB exposure at the above exposure amount through the opening.

Next, during the second exposure, the positions between the slits are adjusted to form a basic pattern (for example, width 0.4 μm, length 1.0 μm), and furthermore, the center part of each basic pattern at the second exposure extends to the joint part of each basic pattern at the first exposure (i.e., the center part of each basic pattern at the time of the first exposure). The position is shifted (by one pitch), and EB exposure is performed again, for example, at the above-mentioned exposure amount of 2.0XIO bow coulombs/cra.

As described above, in the present invention, when performing EB exposure of a fine width pattern, the EB exposure is performed in two steps, so that the exposure amount per time is lower than the exposure amount in the above-mentioned prior art (for example, 3.OX 10- The exposure amount (e.g., 2. OX 10-5 coulombs/cot) can be considerably smaller than the 1. Since it is shifted so that it is located at the joint part of each basic pattern at the time of the first exposure, the joint part formed at the joint part of each basic pattern at the time of the first exposure is the same at the time of the second exposure. This is compensated for by the central portion of each basic pattern, and as a result, the final exposure pattern after the second exposure can have almost no waviness or thickening as in the prior art. In this case, it is better to make the basic pattern at the second exposure a little narrower (0.4 μm in the above example) than the basic pattern at the first exposure. The thickness of the exposure pattern can be further reduced.

As described above, the exposure pattern formed after the double EB exposure has almost no waviness or thickening as shown in FIG. 1(d), and as shown in FIG. 1(a). The resulting design pattern has a shape that is almost defective, and the pattern accuracy is significantly improved.

〔Effect of the invention〕

According to the present invention, when performing EB exposure of a pattern with a fine width such as a submicron pattern, the undulation or thickening of the pattern after exposure due to increasing the exposure amount is almost eliminated, and the height almost matches the design pattern. It becomes possible to form an exposure pattern with high precision, and a remarkable effect can be obtained in that the overall exposure time does not increase as the exposure amount per exposure decreases.

[Brief explanation of drawings]

1(a) to 1(d) are diagrams illustrating an exposure method as an embodiment of the present invention; FIGS. 2(a) to 2(c) are diagrams illustrating an exposure method according to a prior art; 3(a) and 3(b) are diagrams showing another example of the exposure method according to the prior art. (Q) Design turn (b) Divided i4 turn during first exposure (C) Divided pattern during second exposure FIG.

Claims (1)

[Claims] 1. When exposing a fine-width pattern with an electron beam formed into a basic pattern of variable size, the fine-width pattern is exposed twice, and at that time, the second exposure A method for exposing a fine width pattern, characterized in that the central part of each basic pattern when performing the first exposure is shifted to the joint part of each basic pattern when the first exposure is performed. 2. The exposure method according to claim 1, wherein the width of each basic pattern when performing the second exposure is set narrower than the width of each basic pattern when performing the first exposure. .