JP2005268612A - Pattern formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pattern forming method capable of forming a fine hole pattern while improving the dry etching resistance of a resist.
A step of forming a first resist film on a film to be etched, a step of patterning the first resist film, a step of forming a second resist film on the first resist film, Etching back the second resist until the upper surface of the first resist film is exposed, and exposing the entire surface using light having a wavelength such that the first resist film is exposed and the second resist film is not exposed And a step of removing the exposed portion of the first resist film, and a step of patterning the film to be etched using the remaining portion of the first resist film and the second resist film as a mask.
[Selection] Figure 1

Description

  The present invention relates to a pattern forming method for patterning a film to be etched by photolithography.

In the formation of a fine pattern using a photoresist for semiconductor fine processing, the wavelength of light used for exposure becomes shorter year by year as the miniaturization progresses. ArF laser light (exposure wavelength 193 nm) has already been used for mass production, and F ₂ laser light (exposure wavelength 157 nm) has been studied for next-generation processes.

  This resist used for 157 nm light is known to contain fluorine in order to reduce light absorption. On the other hand, there is a drawback that dry etching resistance is poor by containing fluorine. Currently, the resolution of the line system is about 60 nm while clearing these problems, and the film thickness necessary for the base processing can be secured. Various hole-based pattern forming methods have been proposed (see, for example, Patent Documents 1 to 3).

JP-A-2-53060 Japanese Patent Laid-Open No. 3-136233 Japanese Patent Laid-Open No. 7-111237

  However, with respect to the Hall system, the resolution performance of the stepper cannot be obtained, and miniaturization is very difficult. Further, since the film to be etched is thicker than the line system, the required resist film thickness is also required to be thicker than that of the line system. Therefore, for the formation of a hole-based fine pattern, a shrink method using thermal flow of a resist, a two-layer process method using a Si-containing resist, and the like have been proposed. However, even if these methods are used, the resolution of the Hall system is only about 80 mm.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a pattern forming method capable of forming a fine hole pattern while improving the dry etching resistance of a resist. is there.

  The pattern forming method according to the present invention includes a step of forming a first resist film on a film to be etched, a step of patterning the first resist film, and forming a second resist film on the first resist film. A step of etching back the second resist until the upper surface of the first resist film is exposed, and light having a wavelength such that the first resist film is exposed and the second resist film is not exposed. A step of exposing the entire surface, a step of removing the exposed portion of the first resist film, a step of patterning the film to be etched using the remaining portion of the first resist film and the second resist film as a mask, Have Other features of the present invention will become apparent below.

  According to the present invention, a fine hole pattern can be formed while improving the dry etching resistance of a resist.

  Hereinafter, a pattern forming method according to an embodiment of the present invention will be described with reference to FIG.

  First, as shown in FIG. 1A, a silicon oxide film 12 to be etched is deposited to 400 nm on a silicon substrate 11 by a CVD method.

  Next, as shown in FIG. 1B, an organic antireflection film 13 is formed on the silicon oxide film 12. The organic antireflection film 13 is optimized for light having a wavelength of 157 nm and the silicon oxide film 12 which is a base film.

  Next, a fluorine-containing resist film 14 that is a first resist film is formed on the organic antireflection film 13 by spin coating to a thickness of 200 nm. Here, when the fluorine-containing resist film 14 is positive and uses 157 nm light, the absorption coefficient for light with a wavelength of 157 nm is about 1/2 / so that the transmittance at the resist bottom portion is about 50%. A chemically amplified resist of μm is used. However, it is preferable to use a chemically amplified resist having an absorption coefficient of 1.5 / μm for light having a wavelength of 157 nm.

  Next, as shown in FIG. 1C, the fluorine-containing resist film 14 is patterned. Specifically: First, after heat treatment, exposure is performed with 157 nm light through a photomask. At this time, a photomask having a pattern in which a portion where holes are to be formed later is shielded by Cr is used. After the exposure, PEB is performed, solubilized in alkali, and developed with an aqueous TMAH solution to form a fluorine-containing resist film 14. As a result, the fluorine-containing resist film 14 remains on the portion where holes are to be formed later. In addition, since the fluorine-containing resist film 14 has a low light transmittance, the cross-sectional shape becomes a taper, and collapse can be suppressed.

  Next, as shown in FIG. 1D, a novolac resist film 15 having excellent etching resistance is formed as a second resist film on the fluorine-containing resist film 14 by spin coating to a film thickness of 300 nm. Thereafter, heat treatment is performed. Here, as the second resist film, another resin containing a benzene ring such as a polyhydroxystyrene resin can be used instead of the novolac resin.

Next, as shown in FIG. 2 (a), until the upper surface of the fluorine-containing resist film 14 is exposed, a novolac resist film 15 is etched back by N _{2/0 2} gas plasma.

  Next, as shown in FIG. 2B, the entire surface is exposed with light having a wavelength of 157 nm. Here, the fluorine-containing resist film 14 is exposed to light of 157 nm, but the novolac resist film 15 is not exposed to light of 157 nm. In addition, since the novolac resist film 15 has an absorption coefficient of 8 / μm or more for light having a wavelength of 157 nm, the portions other than the exposed portion on the upper surface of the fluorine-containing resist film 14 are not exposed. Therefore, only the upper surface of the fluorine-containing resist film 14 and its lower region 16 are exposed to light and become soluble in alkali.

  Next, as shown in FIG. 2C, after PEB (post exposure bake) is performed again, development is performed with a TMAH (tetramethylammonium hydroxide) aqueous solution. Thereby, the upper surface of the fluorine-containing resist film 14 and its lower region 16 are removed, and the opening 17 is formed.

  Finally, using the remaining portion of the fluorine-containing resist film 14 and the novolac resist film 15 as a mask, the silicon oxide film 12 is patterned to form holes 18.

  As described above, in the pattern forming method according to the embodiment of the present invention, the 157 nm fluorine-containing resist film 14 having excellent resolution but poor dry etching resistance, and a novolak system having excellent dry etching resistance but low resolution. A resist film 15 is combined. Thereby, since the diameter of the hole 18 finally formed is determined by the diameter of the upper surface of the fluorine-containing resist film 14, a fine hole can be opened. Further, the dry etching resistance can be improved as a whole by covering the surface with a novolac resin having excellent etching resistance.

It is sectional drawing (the first half) of the pattern formation method which concerns on embodiment of this invention. It is sectional drawing (latter half) of the pattern formation method which concerns on embodiment of this invention.

Explanation of symbols

11 Silicon substrate 12 Silicon oxide film (etched film)
13 Organic antireflection film 14 Fluorine-containing resist film (first resist film)
15 Novolac resist film (second resist film)
16 Upper surface of fluorine-containing resist film and lower region 17 Opening 18 Hole

Claims (3)

Forming a first resist film on the film to be etched;
Patterning the first resist film;
Forming a second resist film on the first resist film;
Etching back the second resist until the upper surface of the first resist film is exposed;
Exposing the entire surface using light having a wavelength such that the first resist film is exposed and the second resist film is not exposed;
Removing the exposed portion of the first resist film;
A pattern forming method comprising: patterning the etching target film using the remaining portion of the first resist film and the second resist film as a mask. As the first resist film, a resist having an absorption coefficient of 1-2 / μm for light with a wavelength of 157 nm is used.
As the second resist film, a resist having an absorption coefficient of 8 / μm or more for light with a wavelength of 157 nm is used.
The pattern forming method according to claim 1, wherein light having a wavelength of 157 nm is used as the light.   3. The pattern forming method according to claim 1, wherein a novolac resin or a polyhydroxystyrene resin is used as the second resist film.

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