JPH0636343B2 - X-ray generator - Google Patents

Description

The present invention relates to an X-ray generator for use in X-ray lithography, which is a semiconductor processing technique.

[Conventional technology]

X is a new microfabrication technology for manufacturing large-scale integrated circuits.
X-ray lithography using X-ray has been attracting attention.

FIG. 4 is a schematic diagram showing an X-ray lithographic apparatus. In the figure, 1 is a power supply device including a capacitor and a charging device, 2 is a connection cable, 3 is a discharge tube for X-ray generation, 4 is an X-ray transmission window made of a beryllium plate, and 5 is an exposure device. Inside the exposure device 5, an exposure unit composed of a mask pattern in which a light shielding material 7 is provided on a mask substrate 6 and a resist 9 provided on a semiconductor substrate 8 is installed on a support 10.

The inside of the exposure device 5 is evacuated by a vacuum pump 12 via a valve 11 and then replaced with helium gas supplied from a helium gas container 13 having a large X-ray transmittance.

The inside of the discharge tube 3 is evacuated through a valve, and then,
An X-ray generating gas (eg, argon, neon, krypton) 14 is supplied to generate X-rays in the discharge tube 3.

In this apparatus, the X-rays generated in the discharge tube 3 pass through the X-ray transmission window 4 through the portion of the mask 6 where the light shielding material 7 is not provided and are incident on the resist 9, so that the resist 9 is masked. The pattern drawn in 6 is transferred.

The plasma X-ray source described in the present invention is a gas puff type that uses a gas that is a gas at room temperature according to the X-ray generation method (S60 National Conference of the Institute of Electrical Engineers of Japan S.5-1), a plasma focus type, a vacuum that uses a solid or liquid. Spark type (JP-A-57-19194
8 gazette). In both cases, an X-ray generating substance consisting of gas, liquid, and solid is supplied, and characteristic X-rays from this substance are X-rayed.
It is used as a radiation source. The X-ray wavelength will also be determined by the substance used. When the wavelength of X-rays is 14 Å or more, the X-ray transmittance of most substances becomes small and the resist 9 is not exposed. On the other hand, when the X-ray wavelength is 3 Å or less, it becomes difficult to block X-ray transmission, and the pattern contrast becomes insufficient. Therefore, X-rays having a wavelength of 3 to 14Å can be used for X-ray lithography, and X-rays in this wavelength range are called soft X-rays.

FIG. 5 is a graph showing the relationship between the wavelength of the soft X-ray, the X-ray transmission window 4, the optical path in the exposure device 5, the transmittance of the resist substrate 6 and the like. From this graph, it is desirable to use a substance having a shorter wavelength and a higher transmittance as the wavelength becomes shorter. On the other hand, tantalum, tungsten, platinum, gold, etc. are used as the light-shielding material 7 for forming the pattern.
The transmittance of 0.5 μm) is shown in FIG. It can be said that the transmittance is preferably 10% or less for the purpose of shading. In order to increase the contrast of the pattern exposed to the resist 9 from FIGS. 4 and 5, the wavelengths shown by diagonal lines in FIG. 5 (4.3 to 5.6Å)
It is desirable to use a substance that can generate X-rays in the area.
For tantalum, tungsten, platinum, etc., which are used as other light-shielding substances, the wavelength range is calculated in the same manner, and the wavelength range applicable to these light-shielding substances is 4.8 to 5.3.
Limited to Å.

[Problems to be solved by the invention]

Conventionally, as characteristic X-ray generating substances, aluminum (Japanese Patent Application Laid-Open No. 57-191948), neon, and silicon (Proceedings of the nationwide convention of Showa 1984, Announcement No. 1-P-W-3, 1P-)
W-4), Argon, Krypton (J.Appl.Phys.50)
(7) P. 4532) has been used, and phosphorus may be used. The wavelength range of these characteristic X-rays is aluminum K line 8.4 Å and neon Kα line 13.5, respectively.
Å, Silicon Kα ray 7.1 Å, Argon Kα ray 4.0 Å,
The Kα line of Krypton is 7.8Å and the Kα line of phosphorus is 6.2Å.
Of these, none of them can obtain the shaded wavelengths shown in FIG. The only substances having characteristic X-rays in this range are Mo Lα line 5.4Å and sulfur Kα line 5.4Å. In order to use these as plasma X-ray sources, one must rely on vacuum sparks using these materials as the electrodes themselves. But,
In this method, the consumption of the electrode, that is, the light emitting material has been a serious problem.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide an X-ray generating substance and a supply method which can be applied to any system considered as an X-ray source for lithography and which can obtain high contrast. Especially.

[Means for solving problems]

The above object is achieved by heating solid sulfur at room temperature, utilizing the vapor pressure characteristic of sulfur, and supplying it as sulfur vapor into an X-ray generation container in vacuum.

[Action]

FIG. 7 shows the vapor pressure characteristic of sulfur in relation to temperature. Sulfur is a solid at room temperature and has a melting point of about 112-1.
The boiling point at 19 ° C is about 444.7 ° C.

FIG. 8 shows an example of a case where the inter-electrode discharge characteristics in vacuum are obtained from the vapor pressure characteristics of FIG. 6 in relation to temperature.

For example, when sulfur is heated in vacuum to control the temperature to 200 ° C., the degree of vacuum in the vacuum container is maintained at about 1 Torr from FIG. In other words, it is the same as enclosing 1 Torr of sulfur vapor. The inter-electrode discharge voltage at this time is close to the minimum value of 1 kV or less from FIG. Therefore, when the electric charge charged on the power supply side is injected by the external switch or the like, the electric current is easily discharged between the electrodes and a large current is conducted. Due to this large current discharge, sulfur vapor is turned into plasma between the electrodes, causing a Z pinch, and characteristic X-rays of sulfur are emitted. That is, if sulfur vapor is used as a characteristic X-ray generating substance, it can be applied to various systems as a plasma X-ray source, and since a wavelength optimum for exposure can be obtained, high-contrast transfer is possible.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. First
The X-ray generating discharge tube 3 shown in the figure is a plasma focus discharge tube which is one type of plasma X-ray source. An X-ray transmission window 4 separates the exposure apparatus 5 described in the prior art. Inside the discharge tube 3, coaxial electrodes 16 and 17 and a heating device 18 are installed via an insulator 15. One end of the electrodes 16 and 17 has an external power supply capacitor 1
9 and switch 20 are connected. Heating device 3
Is connected to an external heating power source (not shown) and a temperature control device through a sealed terminal, and the temperature is controlled from the outside. A heat insulating material 21 and a radiator 22 are installed between the discharge tube 3 and the exposure device 5 so that the temperature of the discharge tube 3 due to heating is not transmitted to the exposure device 5.

A container 24 is installed from a part of the discharge tube 3 to communicate with the outside via a valve 23, and a heating control power supply (not shown) is also connected to the heating device 25 heated by the heating device 25. Sulfur 25 is sealed in the container 24 as a solid, liquid, or gas.

An operation example will be described below. First, solid or powdery sulfur is put into the container 24, the valve 23 is opened, and the container 24 and the discharge tube 3 are exhausted from the exhaust port 27. Then valve 2
3 is closed and the heaters 18 and 25 are turned on to turn the container 2
4. Heat the inside of the discharge tube 3. For example, heating temperature is 200 ℃
If controlled to a certain degree, some of the sulfur in the container 24 will be gas,
It is in a liquid state. If the valve 23 is opened in this state,
The sulfur in the container 3 is sealed in the discharge tube 3 as steam. When the desired sulfur vapor is filled, the valve 23 is closed.

The charge charged in the power supply capacitor 19 is closed by the switch 20, and a voltage is applied between the electrodes 16 and 17. As shown in FIG. 7, since the discharge pressure is low in the temperature range of 200 to 300 ° C., arc discharge occurs on the surface of the interelectrode insulator 15. This arc is accelerated by the magnetic field generated by the current flowing through the coaxial electrode to the lower end in the figure, jumps out at the end portion, generates a Z pinch on the axis of the electrode, and becomes a spot-shaped light source. The characteristic X-rays of sulfur are emitted. A desired mask pattern is transferred from the characteristic X-rays emitted from this light source to the resist 9 in the exposure device 5 through the X-ray transmission window 4 such as beryllium. Since the light source in this case has a wavelength of about 5Å which is the characteristic X-ray of sulfur, there is little attenuation of the optical path including beryllium 4, etc.
High-contrast transfer with large attenuation is possible.

According to the present embodiment, since solid sulfur at room temperature can be used as a gas for X-ray generation, it should be used in place of the X-ray generation gas such as argon, neon and krypton used in the conventional plasma focus system. There is an effect that can be done.

Another embodiment according to the present invention is shown in FIG. The exposure device 5 is the same as that shown in FIG. One electrode 28 of coaxially arranged electrodes 28, 29 provided inside the discharge tube 3.
A gas passage 30 is provided in the central portion of the, and is usually called a gas puff type discharge tube. Also in this case, as in FIG. 1, the inside of the discharge tube 3 is heated by the heating device 18, and the sulfur heated by the heating device 25 is opened between the electrodes 28 and 29 in synchronization with the discharge start time to open the high-speed valve 31. , Which supplies sulfur vapor, which is an X-ray generating substance, through the gas passage 30,
Also in this case, a Z pinch is caused by the discharge between the electrodes, and the characteristic X-ray of sulfur can be emitted.

According to the present embodiment, it is sufficient to heat the discharge tube to the extent that sulfur does not become solid at the portion that serves as the gas passage, and there is an effect that the heating temperature of the discharge tube itself can be lowered.

Still another embodiment of the invention is shown in FIG. The electrodes 34 and 35 in the discharge tube 3 are vacuum spark electrodes which are one type of plasma X-ray source. Generally, in the case of the vacuum spark type, the electrodes themselves are vaporized by the discharge between the electrodes to become plasma, and Z-pinch is caused by the magnetic force of the current, and a normal metal is used. In this system, sulfur can be used as a solid, but since it is an insulator and has a low melting point, it may be dissolved by discharge, and the supply method is a problem. In the present invention, sulfur is supplied by sulfur vapor. In FIG. 3, the heating device 18 is installed near the electrodes,
If the temperature condition that exists as sulfur vapor in the discharge tube 3 can be obtained, the effect does not change at any position.

Especially in the vacuum spark type, Z pinch is said to occur even if the distance between the electrodes is short, and the Z pinch position accuracy is good. For this reason, there is a feature that exposure can be performed in the circumferential direction of the discharge tube 3.

According to the present embodiment, there is an effect that sulfur vapor can be applied to the vacuum spark type plasma X-ray source.

〔The invention's effect〕

As described above, in short, the present invention is to discharge a characteristic X-ray from high temperature arc plasma by performing pulsed large current discharge between electrodes filled with sulfur vapor as a luminescent substance, The optimum wavelength characteristic X
X-ray source suitable for lithography can be used because it is possible to use a wire, and it is possible to stably supply the vapor by controlling the sulfur reservoir to a constant temperature, and there is no problem of consumption of the luminescent substance. Can be provided.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an embodiment of the present invention, FIG. 2, FIG.
FIG. 4 is a partial sectional view of another embodiment of the present invention, FIG. 4 is a schematic view showing a prior art, and FIGS. 5 to 8 are explanatory views for explaining the present invention. 3 ... Discharge tube, 4 ... X-ray transmission window, 5 ... Exposure device, 16, 1
7 ... Electrode, 18, 25 ... Heating device, 21 ... Heat insulating material, 22
… Radiator, 26… Sulfur.

Front page continuation (72) Inventor Kunio Hirasawa 4026 Kujimachi, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Ltd. (72) Inventor Yoshio Watanabe 1-280, Higashi Koigakubo, Kokubunji City, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Yasuo Kato 1-280 Higashi Koigakubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (3)

[Claims] 1. An X-ray generator used for X-ray lithography using an X-ray shielding material as a mask, wherein sulfur vapor is used as the X-ray generating material in a container accommodating a discharge electrode. X-ray generator. 2. An X-ray generator according to claim 1, wherein a heating device is provided in the container as a means for supplying the sulfur vapor. 3. The X-ray generator according to claim 1, wherein a heating device for heating sulfur is provided outside the container, and the sulfur vapor generated by the heating device is introduced into the container. Line generator.