JP2570803B2 - Pattern formation method - Google Patents

Description

The present invention relates to pattern formation suitable for lithography for transferring a fine pattern such as an electronic circuit pattern onto a wafer surface when manufacturing semiconductor elements such as ICs and LSIs. More particularly, the present invention relates to a pattern forming method that enhances the effective sensitivity of a resist when X-rays having a wavelength of about 1 ° to 150 ° are used.

(Prior art) Recently, in an exposure apparatus for manufacturing semiconductor devices such as ICs and LSIs, X-rays having a wavelength of, for example, about 1 mm to 150 mm that can be printed with higher resolution have been used as semiconductor devices become more highly integrated. Various exposure apparatuses have been proposed.

This so-called X-ray lithography is based on the inherent properties of X-rays such as straightness, incoherence and low diffraction, and has many advantages over conventional lithography using visible or ultraviolet light. ing. Therefore, in recent years, attention has been paid to lithography for submicron and lithography for quarter micron as a powerful means. X-ray lithography has many advantages over lithography using visible light or ultraviolet light. There were problems such as difficulty.

As a resist for X-ray lithography, there is, for example, polymethyl methacrylate (PMMA) as a positive type.

As the negative type, for example, chloromethylstyrene (CM
S) there.

All of these resist materials are organic polymer materials.Positive resist materials have problems such as sensitivity and dry etching resistance, and negative resist materials have problems such as low resolution caused by swelling of the resist film during development. It has become.

Among these problems, one of the most serious problems in the X-ray lithography is sensitivity.

Usually, the X-ray utilization efficiency of the resist in the X-ray lithography is said to be 0.3% or less, which lowers the sensitivity. For example, in the case of PMMA, the effective sensitivity using PdKa rays as X-rays is about 1000 to 2000 mJ / cm ² .

Here, the sensitivity is indicated by the amount of X-ray irradiation at the time of exposure. That is, the sensitivity is as low as the irradiation amount. High-sensitivity resist and chloromethylated polystyrene (CMS, manufactured by Toyo Soda), but effective sensitivity is about 100 mJ /
It is cm ^2.

At present, it is desired to reduce the effective sensitivity of the X-ray resist to 10 mJ / cm ² or less.

However, it is generally very difficult to increase the sensitivity of the resist.

(Problems to be Solved by the Invention) The present invention relates to a resist made of an organic polymer material,
By using a new resist that has performance that has not existed before, such as non-charging properties, high thermal conductivity, and high dry etching resistance, the effective sensitivity of the resist, especially when X-rays are used, is enhanced. Another object of the present invention is to provide a pattern forming method capable of performing high-performance pattern transfer.

(Means for Solving the Problems) When transferring a pattern irradiated with X-rays to a resist layer, the main composition of the resist is made of graphite fluoride, and ultraviolet rays or X-rays are irradiated during X-ray irradiation to the resist. And / or irradiating visible light to form a pattern on the resist layer.

(Embodiment) FIG. 1 is a schematic view of an embodiment when the pattern forming method of the present invention is applied to an X-ray exposure apparatus.

In FIG. 1, reference numeral 1 denotes an X-ray source such as a metal (Pd, Rh, Mo,
W, Cn, Al, Si etc.) K, L characteristic line, wavelength is 4 ~ 13Å
It emits a degree of light.

Reference numeral 2 denotes an auxiliary light source that emits ultraviolet light or visible light, such as a mercury lamp, a xenon lamp, or a black light.
Halogen lamps and the like. 3 is an annular mask frame made of quartz,
It is made of Pyrex, stainless steel, silicon, etc. Reference numeral 4 denotes an X-ray transmission film made of polyimide, SiN, AlN, SiC or the like. Reference numeral 5 denotes a mask pattern provided on the surface of the X-ray transmission film 4 and made of Au, Pt, W, Mo, or the like.

Reference numeral 6 denotes a resist which is mainly composed of graphite fluoride (CF).

Reference numeral 7 denotes a wafer made of silicon, gallium arsenide, glass, or the like.

In this embodiment, the mask pattern 5 is irradiated with X-rays generated from the X-ray source 1, and the mask pattern 5 is
Transcribed to At this time, during the X-ray irradiation,
The light flux from the resist 6 is irradiated on the surface of the resist 6 through the mask pattern 5 in the same direction as the X-ray source 1.

In the figure, the hatched portions of the resist 6 are pattern exposure portions by X-rays.

FIG. 2 shows the state of the pattern after the mask pattern 5 irradiated with X-rays in FIG. 1 is transferred to a resist on the wafer surface 7 and the wafer 7 is developed.

 In this embodiment, a negative pattern is shown.

As described above, in this embodiment, while the resist 6 containing graphite fluoride (CF) as a main component is irradiated with X-rays, the ultraviolet rays (2000
Å4000 °) and / or a predetermined amount of visible light (4000 to 8000 °), thereby increasing the effective sensitivity of the resist.

The resist material in the present embodiment is an inorganic compound mainly composed of fluorinated graphite (CF), and in principle, fluorine (F) is separated (returns) into carbon by X-ray irradiation. . Carbon is excellent in conductivity, high thermal conductivity, high dry etching resistance, and ashing property, and the present invention is characterized by utilizing this property.

In the present embodiment, since ultraviolet light and visible light are unnecessary for patterning, these lights may be irradiated on the resist 6 surface, for example, from an oblique direction without passing through the mask pattern 5.

In this embodiment, it is effective that the ultraviolet light and the visible light correspond to the absorption specific to the reducing agent and the fluorinated graphite.

Further, it is desirable that the irradiation amount of the ultraviolet light or visible light to be irradiated is equal to or less than a threshold value for forming a pattern.

The fluorinated graphite (CF) used in this embodiment is prepared by fluorinating ultrafine graphite (carbon) powder. The granularity at this time is distributed to about 0.05 μ, but may be finer.

It is necessary to form a film of fluorinated graphite using some means. For example, after being dispersed and suspended in a binder material, the film is formed using a coating means (a bar coat, a demep coat, a spin coat, a spray coat, etc.).

Gelatin, casein, PVR, P as binder material
VP, CMC, polyacrylic acid, acrylic acid, gum arabic, nylon, novolak and the like, water, alcohol, ketone, aqueous alkali solution, and soluble resin are suitable. It is also effective to add a halogen acceptor as one of means for stabilizing the latent image, that is, as a means for increasing the sensitivity.

Examples of the halogen acceptor include colloids such as gelatin and casein; aluminum chelate compounds such as aluminum di (isopropoxide) monomethyl ether acetate; aluminum di (butoxide) monoethyl acetate; aluminum tris (ethyl acetoacetate); There are sodium zonite and Lewis.

Further, the addition of a reducing agent is effective as a sensitizer, for example, diphenylamine, hydroquinone, catechol, pyrogallol, P-dimethylaminobenzaldehyde, 1,3
There are single agents and complex agents such as diphenylacridine, chlorhydroquinone, ascorbic acid, P-aminophenol, N-methylparaaminophenol, P-phenylenediamine, glycine and the like.

 Next, specific examples of the resist according to the present invention will be described.

(Example 1) 40 parts of fluorinated graphite, PVA (polyvinyl alcohol) 20
Parts, water 40 parts, ethyl alcohol 10 parts with a ball sill 100
The resist emulsion was adjusted by mixing for hours.

The above emulsion was applied on a silicon wafer provided with an oxide film by about 2 μm using a spinner, and then dried at 50 ° C. for 1 hour to form a resist film.

Light irradiation was performed with an auxiliary light source (xenon lamp) through a quartz window outside the X-ray exposure apparatus (chamber).

The X-ray source is an L line of Pd (palladium) with a characteristic line of 4.4 °.

The mask material for pattern formation is 2 μm thick of aluminum nitride (AlN), and the mask pattern is 0.6 μm thick of tungsten (W).

X-rays were irradiated at 20 KV 48 mA for 120 minutes, and xenon light was simultaneously irradiated on the resist surface with 0.5 mW through a mask pattern.

A black negative resist pattern was obtained by developing with warm water at 40 ° C. for 3 minutes.

Conventionally, when only X-rays were used for irradiation, it took 5 hours to form a pattern.
A five-fold sensitization was measured.

(Example 2) Diphenylamine 2 and hydroquinone 2 were added to a binder material composed of Hooker graphite 30, casein 10 and water 50 ± PA10 parts.
Parts were added and mixed.

The above composition was applied on a silicon wafer provided with an oxide film using a spinner to form a resist film having a thickness of about 2 μm.

An auxiliary light source (ultra high pressure mercury lamp) was provided in the X-ray exposure chamber (2 × 10 ⁻³ torr) near the X-ray source. Rh as X-ray source
The wavelength of the characteristic line of the (rhodium) L line is 4.6 °.

The mask material is 6μ thick polyethylene terephthalate,
The mask pattern is 0.8 μm thick of gold (Au). X-ray is 20K
0.1 mW of UV light (3650, 4047, 4358Å) at V, 48 mA for 60 minutes
/ Sec at the same time on the resist surface through the mask pattern.

After developing with NaOH, 0.5% aqueous solution, 30 ° C. for 3 minutes, a black negative resist pattern was obtained.

Conventionally, since only X-rays were irradiated, it took about 3 hours, but in the present example, it took only 1 hour and the sensitization could be increased about 3 times.

(Example 3) A resist composed of 20 parts of Hooker graphite in a binder of 10 parts of phenol novolak and 200 parts of ethyl alcohol as a resist material was spin-coated on a silicon wafer by about 2 μm.

Exposure to X-rays and ultraviolet light was performed under the same conditions as in Example 2. A negative pattern was obtained by developing NaOH 2% at 23 ° C. for 2 minutes.

Conventionally, exposure required 3 hours, but in this case, good results were obtained in 1/3 of 1 hour.

(Example 4) Al was used as an X-ray source by using a resist having the same composition as that of Example 3.
Kα ray, 10 KV, 20 mA, Xenon 0.3 mW as an auxiliary light source, and 2 μm thick AlN as a mask permeable film.

 The exposure time of the mask pattern by X-rays is 40 minutes.

After the same development as in Example 1, a black negative pattern was obtained.

(Effects of the Invention) According to the present invention, a resist containing graphite fluoride as a main component is irradiated with ultraviolet rays and / or visible light during X-ray irradiation, thereby improving the effective sensitivity of the resist. A pattern forming method suitable for lithography capable of pattern transfer can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view of one embodiment when the pattern forming method of the present invention is applied to an X-ray exposure apparatus, and FIG. 2 is a description of a pattern on a wafer surface obtained in the embodiment shown in FIG. FIG. In the figure, 1 is an X-ray source, 2 is an auxiliary light source, 3 is a mask frame, and 4 is an X-ray source.
5 is a mask pattern, 6 is a resist, and 7 is a wafer.

Claims (2)

(57) [Claims] When transferring a pattern irradiated with X-rays to a resist layer, a main composition of the resist is composed of graphite fluoride, and ultraviolet rays and / or visible light are irradiated during X-ray irradiation on the resist. A pattern forming method, wherein a pattern is formed on the resist layer by irradiation. 2. A pattern forming method according to claim 1, wherein the amount of irradiation of said resist with ultraviolet light and / or visible light is set to be equal to or less than a threshold value of said resist.