JPS61138436A - Plasma soft x-ray generator - Google Patents

Abstract

PURPOSE:To enable a plasma soft X-ray generator for use in an X-ray lithography using tantalum as an X-ray shielding material to perform an excellent X-ray lithography by using sulfur as an X-ray generating material. CONSTITUTION:A large current discharge between electrodes 8 and 9 immediately evaporates the sulfur 12 around an electrode 9 and converts it to plasma, generating a characteristic X-ray. The wavelength range of this characteristic X-ray is within an optimum wave length range for tantalum, tungsten, platinum, and gold. Since the characteristic X-ray of sulfur has a wave length shorter than those of the characteristic X-rays of silicon and phosphorus, the transmission factor of the characteristic X-ray of sulfur through an X-ray transmission window 2 or the like is smaller than those of silicon and phosphorus. therefore, the amount of the light incident on a resist can be increased and the contrast of a pattern can be made sufficiently distinct.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a plasma soft X-ray generator used in X-ray lithography, which is a semiconductor processing technology.

[Background of the invention]

X-ray technology is a new technology for microfabrication of semiconductors.
Line lithography is attracting attention.

FIG. 2 is a schematic diagram showing an X-ray lithography apparatus. In the figure, 1 is an X-ray generator, 2 is an X-ray transmission window made of a beryllium plate, and 3 is an optical path. The inside of the optical path 3 is replaced with helium gas having high X-ray transmittance. 4 is a mask attached to the optical path 3, 4a is the base of the mask 4, and 4b is the base 4
A predetermined pattern is drawn by the X-ray shielding material 4b provided in the X-ray shielding material 4b. 5 is a semiconductor substrate, 6 is a resist provided on the semiconductor substrate 5, and the resist 6 is placed close to the mask 4.

In this device, the X-rays generated in the X-ray generating bag W1 are taken out into the optical path 3 through the X-ray transmission window 2, and the X-rays pass through the part of the mask 4 where the light-shielding material 4b is not provided. Since the light is incident on the resist 6, the pattern drawn on the mask 4 is transferred to the resist 6.

Here, in order to perform good X-ray lithography, it is necessary that the amount of light incident on the resist 6 be large and that the contrast of the pattern be sufficient. For this purpose, an X-ray transparent window 2. It is necessary to increase the X-ray transmittance of the optical path 3° by the substrate 4a, etc., and to decrease the X-ray transmittance of the light shielding material 4b. By the way, when the wavelength of X-rays exceeds about 14 Å, the X-ray transmittance of most materials decreases, so the amount of light incident on the resist 6 decreases;
When the wavelength of the radiation is less than about 3 Å, it becomes difficult to block the transmission of the X-rays, resulting in insufficient pattern contrast. For this reason, X-rays with wavelengths of 3 to 14 can be used for X-ray lithography, and X-rays in this wavelength range are called soft X-rays.

Figure 3 shows the wavelength of soft X-rays and the X-ray transmission window 2. Optical path 3゜Base 4
It is a graph showing the relationship between a and transmittance. As is clear from this graph, the shorter the wavelength, the more
etc., the amount of light incident on the resist 6 can be increased. Therefore, if a material with low transmittance for short wavelength soft X-rays is used as the light shielding material 4b, the amount of light incident on the resist 6 can be increased. and the contrast of the pattern can be made sufficient. Therefore, tantalum, tungsten, platinum, and gold are used as the light shielding material 4b.

Figures 4 to 7 show the soft X-ray wavelength and thickness 0.5-
2 is a graph showing the relationship between the transmittance of tantalum, tungsten, platinum, and gold. As is clear from these graphs, in order to increase the amount of light incident on the resist 6 and to obtain sufficient pattern contrast, soft X-rays with a short wavelength and a transmittance of 20% or less are required. , that is, the wavelength range of the shaded part in Figures 4 to 7 (
It is desirable to use only those in the optimum wavelength range). In order to obtain only soft X-rays in such a wavelength range, it is necessary to use a plasma soft X-ray generator as the X-ray generator 1 and utilize characteristic X-rays.

Traditionally, characteristic X-ray generating substances include aluminum (Japanese Unexamined Patent Publication No. 191.948/1982), neon, and silicon (Presentation No. IP-W-3 of the Proceedings of the 1980 National Conference on Applied Physics).
, IP-W-4 (page 276)), argon.

Krypton (J, App, 1. Phys, 50
(7) p, 4532) is used, and phosphorus is also considered to be used, and the wavelength range of these characteristic X-rays is about 6.0 to 8.5 mm for aluminum and about 11.5 mm for neon, respectively. 5 to 13.5 people, silicon about 5.2 to 7.
2 people, argon about 3.1 to 4.2 people, krypton about 6.3 to 7.9 people, and phosphorus about 4.5 to 6.2 people.

Therefore, when aluminum, neon, argon, or krypton are used as X-ray generating substances, the wavelength range of their characteristic X-rays deviates from the optimum wavelength range of tantalum, tungsten, platinum, or gold. When used, the wavelength range of its characteristic X-rays falls within the optimal wavelength range of tantalum, but tungsten, platinum,
When phosphorus is used as an X-ray generating substance, the wavelength range of its characteristic X-rays falls outside the optimal wavelength range of gold, and falls within the optimal wavelength range of tantalum and tungsten.
This is outside the optimal wavelength range for gold. Furthermore, when silicon or phosphorus is used as the X-ray generating substance, the silicon or red phosphorus adheres to the X-ray transmitting window 2, reducing the X-ray transmittance of the X-ray transmitting window 2. Removal is not easy.

[Purpose of the invention]

This invention was made to solve the above-mentioned problems, and it is possible to increase the amount of light incident on the resist, and the contrast of the pattern is sufficient.

Moreover, it is an object of the present invention to provide a plasma soft X-ray generator that can easily remove precipitates attached to an X-ray transmission window.

[Summary of the invention]

In order to achieve this object, the present invention uses a plasma soft In the generator, sulfur is used as the X-ray generating substance.

[Embodiments of the Invention] FIG. 1 is a diagram showing a plasma soft X-ray generator according to the present invention.・In the figure, 7 is a discharge vessel;
The inside is evacuated to a vacuum, and the discharge vessel 7 is provided with an X-ray transmission window 2. Reference numerals 8 and 9 denote a pair of electrodes attached to the discharge vessel 7. The electrodes 8 and 9 are provided facing each other, and one electrode 9 is made of tungsten and has a needle-like shape. Numeral 10 is provided in the discharge vessel 7 and has nine cavities, and the electrode 9 is located in the center of the cavity 10. Numeral 11 is a supply hole communicating with the cavity 10, and molten sulfur 12 is supplied to the cavity 10 through the supply hole 11.

In this device, when a large current discharge is generated between the electrodes 8 and 9, the sulfur 12 surrounding the electrode 9 is immediately evaporated and turned into plasma, generating characteristic X-rays.

The wavelength range of the characteristic X-rays of sulfur is approximately 4.0 to 5.4
Because it is a human being, this wavelength range falls within the optimal wavelength range of tantalum, tungsten, platinum, and gold, and also has the characteristics of sulfur.
The wavelength of the line is shorter than the characteristic X-rays of silicon and phosphorus, so
Since the transmittance of the characteristic X-rays of sulfur through the X-ray transmission window 2, etc. is smaller than the transmittance of the characteristic X-rays of silicon and phosphorus through the X-ray transmission window 2, etc., the amount of light incident on the resist can be increased. In addition, the contrast of the pattern is sufficient.

In addition, the melting point of sulfur is as low as 119°C, and the viscosity of liquid sulfur can be controlled over a wide range by temperature. Furthermore, the boiling point is quite low at 445°C, and it dissolves well in organic solvents such as carbon disulfide and carbon tetrachloride. Even if it adheres to the X-ray transmission window 2, it can be easily removed by heating or using an organic solvent.

Furthermore, since sulfur is a good electrical insulator, even if sulfur adheres to the inner wall of the discharge vessel 7, the discharge vessel 7
The internal withstand voltage will not deteriorate.

Moreover, sulfur has no toxicity or reactivity at room temperature, is easy to store, and is inexpensive.

In addition, in the above-mentioned example, molten elemental sulfur 12
However, hydrogen sulfide or the like may also be supplied. Further, in the above-described embodiments, the plasma generation method is a vacuum gap discharge method, but a gas puff discharge method or a focus discharge method may be used.

〔Effect of the invention〕

As explained above, in the plasma soft X-ray generator according to the present invention, the amount of light incident on the resist can be increased and the contrast of the pattern is sufficient, so that good X-ray lithography can be performed. can. Furthermore, since precipitates adhering to the X-ray transmission window can be easily removed, maintenance is easy. As described above, the effects of this invention are remarkable.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a plasma soft X-ray generator according to the present invention, FIG. 2 is a schematic diagram showing an X-ray lithography apparatus, and FIG.
7 to 7 are graphs showing the relationship between the wavelength of soft X-rays and the X-ray transmittance of tantalum, tungsten, platinum, and gold, each having a thickness of 0.5I1 m, such as an X-ray transmission window. 7...Discharge vessel 8,9...Electrode 10...
・Void 11... Supply hole 12... Sulfur

Claims (1)

[Claims] A plasma soft X-ray generator used for X-ray lithography using a mask using at least one of tantalum, tungsten, platinum, and gold as an X-ray shielding material, characterized in that sulfur is used as the X-ray generating material. Plasma soft X-ray generator.