JP2549317B2 - Method of forming resist pattern - Google Patents

Description

The present invention relates to a method for forming a pattern of a resist used for manufacturing semiconductor elements, ICs, LSIs, VLSIs and the like.

[Prior Art] Conventionally, as the degree of integration of LSIs and VLSIs has advanced, pattern formation using a single-layer resist has become unable to cope with these integrations. Therefore, in order to cope with the integration, pattern formation using a multilayer resist has been performed.

For example, in Japanese Examined Patent Publication No. 63-60893, a lower layer 22 made of a substance that can be etched by plasma is formed on a substrate 21 as shown in FIG. 2, and a resist containing a silicon compound is formed thereon. The liquid is applied to form the upper layer 23 (Fig. 2a).

Next, the upper layer 23 is pattern-exposed by the electron beam 25 (first
2b), the unexposed portion of the upper layer 23 is removed by heat treatment, vacuum treatment or vacuum heat treatment to form an etching mask 26 (FIG. 2c). Then, the etching mask
The lower layer 22 is etched by plasma treatment using 26 as a mask to form a resist pattern (FIG. 2d).

[Problems to be Solved by the Invention] The resist forming method described in Japanese Patent Publication No. 63-60893 is a method of forming a resist pattern consisting of two layers, and has a higher resolution and a finer pattern than a method of forming a single layer resist pattern. Although the pattern can be formed, the resist must be applied twice, and contaminants are mixed in during the resist application, which causes a defect (for example, disconnection) in the pattern formed on the substrate. There is.

Further, since the resist is composed of two layers, there is a defect that defects such as insufficient adhesion occur at the interface between the upper layer and the lower layer. Furthermore, a resist material that may react at the interface between the resist layer and the resist layer cannot be used, and generally, a silicon-containing resist has a complicated structure and requires time and cost for plywood. However, there is a drawback that only very limited materials can be used.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks, and takes advantage of the single-layer resist method capable of preventing contamination from being mixed as compared with the two-layer resist method, and the structure is complicated and high. It is intended to provide a resist pattern forming method which has the advantages of a two-layer resist method capable of forming a fine pattern without using a costly material.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and a method for forming a resist pattern according to the present invention includes the following first method.
It is characterized in that it includes the steps from the fourth step.

As the first step, a polymer containing a functional group having active hydrogen is applied to the substrate to form a resist layer.

In the second step, the surface layer of the resist layer is silylated by reacting the polymer with a silicon-containing low molecular weight compound to form a surface-modified resist layer.

In the third step, the surface modified resist layer is subjected to pattern exposure by irradiation with ionizing radiation, and the exposed surface layer portion or the unexposed surface layer portion is removed by wet development to form a primary resist pattern.

As a fourth step, dry-developing the resist layer between the substrate and the surface layer of the resist layer and in the removed portion of the primary resist pattern by etching with a gas containing oxygen using the primary resist pattern as a mask. Then, a secondary resist pattern is formed.

As the substrate in the first step, Si, SiO ₂ , GaAs, glass, metal or the like can be used, and a light shielding film such as a chromium film, a molybdenum film or a tantalum film is further formed on a transparent plate-like object such as a glass plate. It is also possible to use a laminate of transparent conductive films such as an indium tin oxide (ITO) film and the like, and the polymer is not limited to a commercially available resist or resist solution, but may be a polymer containing a functional group having active hydrogen. Good. The functional group having active hydrogen, a hydroxyl group, an amino group, an amide group, an imide group, a carboxyl group,
Formyl group and the like can be mentioned. Further, as a polymer containing these functional groups, in the case of a positive type, α-methylstyrene: 23.4%, methylmethacrylate: 65.9%, methacrylamide: 1.7% terpolymer (hereinafter abbreviated as TT-3I), Polyvinylferel (abbreviated as PVP), copolymer of methylmethacrylate: 41.0%, vinylphenol: 59.0% (hereinafter abbreviated as CVP-59), two-component polymer of novolac resin and polymethylpentene sulfone (for example, this polymer) RE5000 as a resist having
P, Hitachi Chemical Co., Ltd. product name), novolac resin and o
A two-component polymer of quinonediazide, a two-component polymer of novolac resin and diazomeldrum acid, a novolac resin, polyphthalaldehyde and onium salt
Examples include component polymers.

In the case of a negative type, a two-component polymer of polyvinylphenol and monoazide (for example, MRL as a resist having this polymer, a product name of Hitachi Chemical Co., Ltd.), polyvinylphenol and 3,3'diazidediphenyl A two-component polymer with sulfone (for example, MRS as a resist having this polymer, a product name of Hitachi Chemical Co., Ltd.) and the like can be mentioned.

The coating method of these polymers may be a well-known method such as spin coating, roll coating, or immersion in a solution.

The method of reacting the polymer with the silicon-containing low-molecular compound in the surface layer of the polymer containing a functional group having active hydrogen in the second step to silylate is, for example, vaporization using a gas phase permeation treatment apparatus. The silicon-containing low molecular weight compound can be silylated by diffusing into the polymer.

As shown in Fig. 3, the gas-phase infiltration treatment device is a bell jar.
There is a sample table 32 in 31 and the sample table 32 can be heated to a desired temperature by a heater 33. Further, an ampoule 34 for storing the silicon-containing low-molecular compound is connected so that the bell jar 31 can be filled with the vapor of the silicon-containing low-molecular compound, and the vapor pressure of the silicon-containing low-molecular compound is heated by heating the ampoule 34. Can be adjusted. In addition, a system to degas the inside of the bell jar 31
35, and an N ₂ gas introduction system 36 for expelling the steam filled in the bell jar 31 are connected. Reference A is an aspirator, P is a rotary pump, and G is a vacuum gauge.

With this apparatus, the substrate coated with the polymer can be placed on the sample table 32 in the bell jar 31 to vaporize the low molecular weight compound contained in silicon, and the surface layer of the polymer can be silylated.

As the silicon-containing low-molecular compound used at this time,
Trimethylchlorosilane (hereinafter abbreviated as TMCS), hexamethyldisilazane (hereinafter abbreviated as HMDS), heptamethyldisilazane, trimethylsilyldimethylamine, dimethylsilyldichloride, monomethylsilyldichloride, bis (dimethylamino) dimethylsilane, bis (dimethyl) Amino) methylsilane and the like.

In the third step, the silylated polymer surface layer (surface modified resist layer) obtained in the second step is patternwise exposed to ionizing radiation. Then, the exposed portion or the unexposed portion of the resist surface layer is removed by utilizing the difference in solubility between the exposed portion and the unexposed portion in the developing solution to form a primary resist pattern.

Whether the exposed portion or the unexposed portion is removed depends on the characteristics of the polymer used. For example, when the bond in the polymer is broken by the ionizing radiation, the exposed portion is removed by the developer (positive type). Conversely, when the polymer is crosslinked by ionizing radiation, the unexposed area is removed by the developer (negative type).

The ionizing radiation used at this time is ultraviolet rays, X-rays,
An electron beam or an ion beam can be used. Further, as a developing solution, ammonia water, tetramethylammonium hydroxide or tetraethylammonium hydroxide in water,
It is possible to use one to which at least one of methanol, ethanol, propanol, isopropanol and the like is added.

Further, even when the ionizing radiation is exposed below the surface modified resist layer, only the surface modified resist layer is dissolved in the above-mentioned developing solution, while the solubility of the polymer is small in the developing solution, and therefore it is not removed.

The fourth step is etching with a gas containing oxygen. An example of this etching method is O ₂ RIE.

At this time, since the surface-modified resist layer remaining in the third step serves as a barrier layer against etching, only the portion removed by the development in the third step is etched and a secondary resist pattern is formed. In the present invention, by performing the "dry development" of the third step before the dry development of the fourth step, not only a barrier layer is formed at the time of the dry development, but also unreacted residue remaining on the resist film is formed. The silylating agent can be removed to reduce the formation of residues due to etching with a gas containing oxygen (dry development step).

[Examples] Next, examples of the present invention will be described with reference to FIG. 1, but the present invention is not limited to these examples.

Example 1 A resist layer 12 was formed by applying RE5000P (polymer) to a thickness of 1 to 2 μm on a Si substrate 11 having a size of 20 × 20 mm by a spin coating method (first step).

Next, the sample stage 32 in the bell jar 31 of the vapor phase infiltration treatment apparatus shown in FIG. 3 was previously heated to 78 ° C. by the heater 33, and the Si with resist obtained in the first step was placed on the sample stage 32.
A substrate (sample) was set. Then, after exhausting the air in the bell jar 31, N ₂ gas was put into the bell jar 31, and this N ₂ gas was further exhausted to make the bell jar 31 a vacuum of 3 Toor or less. During this period, the sample temperature was raised to 90 ° C. Next, the HMDS ampoule 34 is heated and HMDS vapor is introduced into the bell jar 31 to raise the pressure in the bell jar 31 to 85 Toor and the surface layer of RE5000P and the silicon-containing low molecular weight compound 14 of HMDS are added for about 20 minutes. The reaction was performed as shown in the figure to obtain a resist having a surface-modified resist layer 13 in which a polymer and Si were bonded (silylated) from the surface layer of RE5000P to a depth of about 1500Å (second step).

After the reaction, after stopping the heating of the sample table 32 and introducing N ₂ gas,
After confirming that the sample temperature was 80 ° C. or lower, the sample was taken out of the bell jar 31.

In this second step, the fact that the silicon atoms of HMDS are bonded in the surface layer of RE5000P (polymer) is confirmed by X-ray fluorescence analysis and
It was confirmed by IR measurement that silicon atoms were present in the polymer. The silylation depth was measured by XPS.

Then, as shown in FIG. 1b, the surface modified resist layer 13 was irradiated with an electron beam 15 to perform pattern exposure. After exposure, tetramethylammonium hydroxide: water: ethanol is 2: 8: 3
Was used as a developing solution to remove the exposed surface layer portion of the surface modified resist layer 13 as shown in FIG. 1c to form a primary resist pattern 16 (third step).

Finally, by O ₂ RIE (reactive ion etching in an oxygen atmosphere), the resist whose exposed surface layer portion has been removed is punched out (etching) to form a secondary resist pattern 17 as shown in FIG. 1d. Since the unexposed surface layer portion forming the primary resist pattern 16 was silylated, it had excellent O ₂ RIE resistance and was hardly etched (fourth step).

Further, the following operation was performed in order to confirm that the Si substrate 11 was etched according to the resist pattern.

The resist residue remained on the upper surface of the Si substrate 11 obtained in the fourth step. Since this was considered to be a resist containing SiO ₂ remaining by O ₂ RIE, Ar ⁺ sputtering was performed to remove the residue. Then etching the Si substrate 11 at least secondary resist pattern 17 as a mask by CF ₄ / O ₂ plasma etching of CF ₄ 95% and O ₂ 5%.

As a result, the Si substrate was uniformly etched to a depth of 11 to 12 μm, leaving a resist layer having a thickness of about 0.6 μm.

(Example 2) MRS was used as a polymer instead of RE5000P, and the first step and the second step were performed in the same manner as in Example 1 to silylate the surface layer of MRS to obtain a surface-modified resist layer. In the third step, the surface-modified resist layer was exposed to ultraviolet rays for pattern exposure, and a developing solution similar to that in Example 1 was used.
On the contrary, the unexposed portion was removed to form a primary resist pattern. Next, as in Example 1, etching was carried out by O ₂ RIE to form a secondary resist pattern.

[Effects of the Invention] As described in detail above, the resist pattern forming method of the present invention is a resist pattern forming method that has the advantages of the single-layer resist method and the double-layer resist method, and according to the method of the present invention, Since the resist is formed by silylating the surface layer of the polymer containing a functional group having active hydrogen, there is little risk of contaminants entering the polymer during coating, defects at the interface between resist layers do not easily occur, and the structure is complicated. A fine resist pattern can be formed without defects by performing wet development and etching with a gas containing oxygen without using a high-cost material.

Further, according to the present invention, the polymer forming the resist layer is not limited to the commercially available resist or resist solution, and therefore, there is an advantage that polymers having various characteristics can be used as the resist layer.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the steps of the resist pattern forming method of the first embodiment. FIG. 2 is a partial cross-sectional view showing the steps of a conventional two-layer resist pattern forming method. FIG. 3 is a schematic view showing a vapor phase infiltration treatment device. 11 ... Substrate, 12 ... Polymer layer 13 ... Surface-modified resist layer, 14 ... Silicon-containing low-molecular compound vapor 16 ... Primary resist pattern 17 ... Secondary resist pattern

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Ueno 5-2 Konakadai, Chiba-shi, Chiba Civil servant, Building No. 3, Building No. 206 Examiner Sadaharu Yoshida (56) Reference JP-A-1-159641 (JP, A) Kai 63-300237 (JP, A) JP 3-154062 (JP, A) JP 2-140749 (JP, A)

Claims (1)

(57) [Claims] 1. A method of forming a resist pattern, which comprises the following first to fourth steps. As the first step, a polymer containing a functional group having active hydrogen is applied to the substrate to form a resist layer. In the second step, the surface layer of the resist layer is silylated by reacting the polymer with a silicon-containing low molecular weight compound to form a surface-modified resist layer. In the third step, the surface modified resist layer is subjected to pattern exposure by irradiation with ionizing radiation, and the exposed surface layer portion or the unexposed surface layer portion is removed by wet development to form a primary resist pattern. As a fourth step, dry-developing the resist layer between the substrate and the surface layer of the resist layer and in the removed portion of the primary resist pattern by etching with a gas containing oxygen using the primary resist pattern as a mask. Then, a secondary resist pattern is formed.