JP2930971B2 - Pattern formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a pattern forming method.

(Prior art) With the miniaturization of semiconductor devices, line widths formed on silicon wafers are becoming submicron, and lithography technology required for processing and performance required for resist materials are becoming increasingly severe. It is becoming something. Regarding the lithography technology required for device fabrication, the current g-line (wavelength 436 nm) to i-line (wavelength 365 nm) and
There is a trend toward shorter wavelengths such as KrF excimer light (wavelength 248 nm). Although resist materials have been developed in response to this tendency, it is not easy to realize a pattern of a lower submicron size of less than 0.5 μm. As a means for solving this problem, a multilayer resist process has been proposed.

However, the conventional resist process can solve the problem of resist transparency by making the upper photosensitive layer thinner, but also causes pinholes, cracks and warpage due to stress generated between different layers, And there are technical problems such as a problem of pattern conversion difference at the time of transfer to a lower layer.

(Problems to be Solved by the Invention) An object of the present invention is to provide a new and highly reliable pattern forming method capable of solving such a conventional problem.

[Configuration of the invention]

(Means for Solving the Problems) The present invention provides a step of applying a hydrophobic resist film on a substrate, and exposing the resist film to a desired pattern to make the surface of the resist film in an exposed region hydrophilic. A step of depositing and depositing a silicon oxide film from a silica supersaturated solution on a fresh aqueous surface of the resist film, and etching a portion of the resist film where the silicon oxide film is not formed on the surface, Patterning a resist film.

(Operation) In a silica supersaturated solution, a silicon oxide film is deposited only on a hydrophilic resist surface region. This silicon oxide film has a dense structure, and the resist film can be favorably patterned using the silicon oxide film as a mask.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 (a) to 1 (d) are sectional views showing the steps of an embodiment of the present invention.

First, a substrate in which, for example, a polycrystalline silicon film 12 is formed on a substrate 11 having irregularities is prepared. The base 11 is formed, for example, by providing a silicon oxide film on a silicon wafer on which elements are formed.

Next, a resist film 13, for example, a methacrylic anhydride resin, which is a resin having an acid anhydride structure, is spin-coated flat (FIG. 1a).

Next, far ultraviolet rays, here, KrF excimer light (wavelength 248n
m) Expose 14 through a mask.

The resist surface in this exposed area is changed from hydrophobic to fresh water, and a hydrophilic resist surface layer 15 is formed (FIG. 1b).

Next, this substrate is immersed in a silica supersaturated solution, and a silicon oxide film 16 is formed only on the hydrophilic resist surface layer 15, for example.
Deposit and deposit about 300 ° (Fig. 1c).

 The aqueous solution of silica supersaturation is prepared as follows.

First, a 40% by weight aqueous solution of hydrosilicofluoric acid (H ₂ SiF ₆ ) is diluted with water to form a 3 mol / hydrofluoric acid hydrofluoric acid solution.
This is filled with silica (SiO ₂ ) and saturated. Then, an aluminum plate (Al) is immersed in this solution to produce a silica supersaturated solution.
The agricultural degree of the hydrosilicofluoric acid solution is not particularly limited to the above value.

 The above reaction is represented by the following equation.

H ₂ SiF ₆ + 2H ₂ O → SiO ₂ + 6HF (1) 2Al + 6HF → 2HlF ₃ + 3H ₂ (2) That is, the HF concentration in the formula (1) is reduced by reacting with HF and consuming it, and the HF concentration is reduced. _Two films are deposited. As the reaction temperature increases, the reaction of (1) proceeds to the right, and the deposition of SiO ₂ increases.

At the current liquid temperature of 35 ° C, a deposit of 300Å occurs in 30 minutes. This silicon oxide film 16 is very dense.

Next, using the silicon oxide film 16 as a mask, the resist film 13 is anisotropically etched by reactive ion etching using oxygen gas (O ₂ ). Then, the polycrystalline silicon film 12 is processed by reactive ion etching using a gas containing chlorine, for example, a Cl ₂ gas.

As described above, since a fine pattern can be realized with a single-layer resist, the throughput is improved.

In addition, since only the surface of the resist has to be exposed in principle, the transmittance with respect to the wavelength of the light source used for the exposure does not matter so much, and excellent resolution can be easily obtained. In addition, since exposure of only the surface of the resist is sufficient, thinning of the resist due to reflection from the underlying pattern or the like can be reduced.

Further, the dry development used in the examples is effective in suppressing a pattern conversion difference due to a variation in the resist film thickness.

Although the aluminum plate is immersed in the above embodiment, for example, an aqueous solution of boric acid (H ₃ BO ₃ ) may be added to a hydrosilicic acid solution saturated with silica as the silica supersaturated solution.

Further, immediately after the exposure, the substrate is immersed in a silica supersaturated solution. However, if desired, the substrate may be baked in the air at 140 ° C. for about 5 minutes, and then immersed in the silica supersaturated solution. This has the function of ensuring the hydrophilicity of the resist in the exposed area.

Further, using a naphthoquinonediazide-novolak diameter resist as a resist film, the exposed sample is heat-treated in a reduced-pressure gas atmosphere of, for example, hexamethyldisilazane,
The resist in the exposed area may be silylated to promote the hydrophilicity of the exposed part resist.

For the exposure, g-line, i-line, X-ray or electron beam can be used in addition to the above KrF excimer light.

2 (a) to 2 (f) are sectional views showing another embodiment of the present invention.

2 (a) to 2 (c) are the same as the methods described in FIGS. 1 (a) to 1 (c).

Thereafter, the resist film 13 is anisotropically etched by reactive ion etching using O ₂ gas, the substrate is immersed again in a supersaturated silica solution, and the silicon oxide film 21 is similarly formed on the surface of the underlying polycrystalline silicon film 12. Deposited and deposited (second
Figure d).

Next, as shown in FIG. 2 (e), the resist film 13 is etched using, for example, a mixed solution of a hydrogen peroxide (H ₂ O ₂ ) solution and a sulfuric acid (H ₂ SO ₄ ) solution, and is further removed by this lift-off. The polycrystalline silicon film 12 is processed using the silicon oxide film 21 as a mask.

This makes it possible to process (reverse processing) the same pattern as the mask using a positive resist.

In addition, the present invention can be variously modified and implemented without departing from the spirit thereof.

〔The invention's effect〕

According to the present invention, a new and highly reliable pattern forming method can be provided.

[Brief description of the drawings]

FIG. 1 is a process sectional view for explaining an embodiment of the present invention, and FIG. 2 is a process sectional view for explaining another embodiment of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-241225 (JP, A) JP-A-60-85526 (JP, A) JP-A-61-107346 (JP, A) JP-A-62 258449 (JP, A) JP-A-64-3363 (JP, A) JP-A-63-300237 (JP, A) JP-A-63-253356 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) G03F 7 / 38,7 / 038

Claims (5)

(57) [Claims] A step of applying a hydrophobic resist film on a substrate; a step of exposing the resist film to a desired pattern to make the surface of the resist film in an exposed region hydrophilic; A step of depositing and depositing a silicon oxide film on an aqueous surface from a silica supersaturated solution; anda step of patterning the resist film by etching a portion of the resist film where the silicon oxide film is not formed on the surface. A pattern forming method, comprising: 2. The pattern forming method according to claim 1, wherein a resin having an acid anhydride structure is used as said resist film. 3. The pattern forming method according to claim 1, wherein the exposure is performed using ultraviolet rays, visible light, X-rays or electron beams. 4. A method according to claim 1, wherein said silica supersaturated solution is an aqueous solution containing hydrofluoric acid, and said silicon oxide film is formed by adding an aqueous solution of Al or boric acid to said silica supersaturated solution. The pattern forming method according to claim 1, wherein 5. The pattern forming method according to claim 1, further comprising, after the patterning step, a step of depositing and depositing a second silicon oxide film from the supersaturated silica solution on the exposed surface of the substrate. .