JPH0237710A - Electron beam direct lithography method - Google Patents

Abstract

PURPOSE:To make it possible to make enough electron beam reach an alignment mark even when an intermediate layer is formed by setting an acceleration voltage of electron beam in a reference position detection process higher than that of electron beam in a pattern lithography process. CONSTITUTION:The acceleration voltage of an electron beam 4a is strongly set in a reference position detection process. Therefore, even if intermediate layers 6, 7 are formed between a resist 3 and an alignment mark 2. A large quantity of electrons in the electron beam 4a reach the alignment mark 2, with the result that sufficient reflection electrons 5 can be obtained. In a pattern lithography process, the acceleration voltage of the electron beam 4b is set at a conventional degree of voltage. As a result, no electrons in the electron beam 4b invade within a substrate which is a basement and no damage caused to devices formed. Therefore, even when an intermediate layer is formed between a resist and an alignment mark, enough electron beam can be made to reach the alignment mark.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron beam direct writing method, which is one of the exposure steps in lithography technology.

[Conventional technology]

FIG. 4 is a sectional view showing a conventional electron beam direct writing method. As shown in the figure, seven alignment marks 2 used for measuring reference positions for overlapping patterns are provided at predetermined positions on a substrate 11 by processing the substrate 1. A resist 3 is formed on the substrate 1 including the alignment mark 2. This resist 3 is scanned with the electron beam 4, and the direction from the alignment mark 2 is
By detecting the j electron 5, the alignment mark 2 is
Detect the position of. The following is the reference position detection step.

After the reference position detection process is completed, using the alignment mark 2 as a reference position, a predetermined pattern is drawn on the register 3 using the electron beam 4 of the same acceleration voltage as in the case of reference position detection. The above is the pattern drawing process. Since this drawing is based on the position of the alignment mark 2, accurate small alignment with the pattern formed on the surface of the substrate 1, which is the underlying pattern, can be performed.

[Problem to be solved by the invention]

The conventional electron beam direct writing method is performed as described above, and the acceleration voltage of the electron beam 4 in the reference position detection step and the pattern writing step is the same.

This acceleration voltage is normally 20 to 30 KV, but this level of acceleration voltage is used when the resist 3 is thick or for flattening the surface between the alignment mark 2 and the resist 3 as shown in FIG. , intermediate 1ii16°7, only a small number of electrons in the electron beam 4 reach the alignment mark 2.

For this reason, there is a problem in that sufficient reffi elements 5 cannot be obtained, the detection accuracy of the alignment mark 2 position deteriorates, and in the worst case, the alignment mark 2 position cannot be detected.

In order to avoid this problem, if the acceleration voltage of the electron beam 4 is increased to about 50 KV, the position of the alignment mark 2 can be detected with high accuracy. However, if the pattern drawing process is performed with this acceleration voltage, the A large number of electrons from the electron beam 4 enter the inside of the device 1, causing a new problem of damaging the device.

This invention was made to solve the above-mentioned problems, and its purpose is to provide an electron beam direct writing method that can accurately detect the position of alignment marks and does not cause damage to manufactured devices. do.

(Means for Solving the Problems) The electron beam direct writing method according to the present invention includes: ``a reference position detection step of detecting an alignment mark position by irradiation with an electron beam; and a pattern drawing step of patterning the Asha resist by irradiating the resist, and the acceleration voltage of the electron beam in the reference position detection step is set higher than the acceleration voltage of the electron beam in the drawing step.

(Function) In this invention, since the acceleration voltage of the electron beam in the reference position detection process is set higher than the acceleration voltage of the electron beam in the pattern drawing process, in the JliF position detection process, when the resist film is thick or Even when an intermediate layer is formed between the resist and the alignment mark, a sufficient electron beam can reach the alignment mark.

(Embodiment) FIG. 1 is a top view showing an electron beam direct writing method which is an embodiment of the present invention. In the same figure, 1 to 3.5 to
7 is the same as the conventional example shown in FIG. 5, so its explanation will be omitted. Reference numeral 8 indicates the 7 alignment mark forming region, 9 indicates the device forming region, 4a indicates the electron beam in the base position detection culm, and 4b indicates the electron beam in the pattern drawing process.

In the reference position detection step, since the acceleration voltage of the electron beam 4a is set strongly at about 50 KV, the resist 3
．． Even if intermediates A6 and 7 are formed between the alignment marks 2, a large amount of electrons in the electron beam 4a reach the alignment mark 2, and sufficient reflected electrons 5 can be obtained, resulting in a highly accurate 7 alignment The position of mark 2 can be detected.

On the other hand, in the pattern drawing process, since the acceleration voltage of the electron beam 4b is set to about 20 to 30 KV as in the conventional case, electrons as wide as the width of the electron beam 4b do not enter into the substrate 1, which is the base. No damage to the device being formed.

In this way, by setting the acceleration voltage of the electron beam 4a in the reference position detection process higher than the acceleration voltage of the electron beam 4b in the pattern drawing process, it is possible to achieve highly accurate reference position detection and regime 1- that does not damage the device. pattern drawing can be realized.

FIG. 2 is a block diagram showing an electron beam lithography apparatus for realizing the electron beam direct lithography method shown in FIG. As shown in the figure, as a power supply to the electron gun 11, 50
Two types of power source 12 for high acceleration of about KV and a power source 13 for low acceleration of about 20 to 30 KV are prepared. It is selectively connected to the power source 13 for use. Although not shown, it is also possible to connect the electron gun 11 to one power source and selectively generate two types of voltages, one for high acceleration and one for low acceleration, from this power source. In addition, 1
4 is a semiconductor wafer, and 15 is a stage on which the semiconductor wafer 14 is placed.

FIG. 3 is a block diagram showing another example of an electron beam direct writing apparatus for realizing the electron beam direct writing method shown in FIG. M1. As shown in the figure, the electron gun is
By connecting the high acceleration power source 12 to the electron gun 11a and the low acceleration power source 13 to the electron gun 11b, two types of electron beam irradiation systems 20a and 20b are provided. . The semiconductor wafer 14 on the stage 15 is placed under the electron beam irradiation system 2Oa in the reference position detection process, and is placed under the electron beam irradiation system 2Oa in the pattern drawing process.
b It is moved downward.

(Effects of the Invention) As explained above, according to the present invention, since the acceleration voltage of the electron beam in the reference position detection step is set higher than the acceleration voltage of the electron beam in the pattern drawing step, the acceleration voltage of the electron beam in the reference position detection step is set higher than that in the pattern drawing step. Even when the resist film is thick or when an intermediate defect is formed between the resist and the alignment mark, a sufficient electron beam can reach the alignment mark.As a result,
The position of the alignment mark can be detected with high precision.

Furthermore, since the acceleration voltage of the electron beam in the pattern drawing process is not as high as the acceleration voltage in the reference position detection process, old scratches are not caused on the manufactured device.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an electron beam direct writing method as an embodiment of the present invention, and FIGS. 2 and 3 are electron beam writing apparatuses for realizing the electron beam direct writing method shown in FIG. FIG. 4 is a cross-sectional view showing a conventional electron beam direct writing method, and FIG. 5 is a cross-sectional view showing problems with the conventional electron beam direct writing method. In the figure, 2 is an alignment mark, 3 is a resist,
4a and 4b are electron beams, 11 is an electron gun, 12 is a high acceleration power source, and 13 is a low acceleration power source. Note that the same reference numerals in each figure indicate the same or corresponding parts. Fig. 1 Fig. 2 2-111 alignment mark 7 3-11-ν nos.

Claims (1)

[Claims] (1) An electron beam comprising a reference position detection step of detecting an alignment mark position by irradiation with an electron beam, and a pattern drawing step of patterning the resist by irradiating the resist with the electron beam using the alignment mark position as a reference. An electron beam direct writing method, characterized in that the acceleration voltage of the electron beam in the reference position detection step is set higher than the acceleration voltage of the electron beam in the pattern writing step.