JPH01102459A - Pattern forming method - Google Patents

Abstract

PURPOSE:To decrease the absorption of excimer laser light in a prescribed photoresist film by forming a fluorescent film on the resist film and projecting the excimer laser light to the resist film through this fluorescent film. CONSTITUTION:The positive type photoresist film 2 of a phenol novolak system is formed on a semiconductor substrate 1. A soln. prepd. by dispersing a fluorescent material (e.g. CaWO4) in an aq. soln. of an org. material (e.g. milk protin casein) is coated on the film 2 to form the fluorescent film 3. The excimer laser light is selectively projected to the film in succession thereto. Fluorescent reaction is thereby generated in the film 3 of the irradiated region and the UV light of a relatively long wavelength is formed. This long wavelength light enters the inside of the film 2. The film 3 is thereafter removed by pure water and the film 2 is developed to form resist patterns 2a.... Since the absorption of the excimer laser light in the film 2 is decreased according to this method, the patterns 2a... having steep side walls and excellent dimensional reproducibility are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pattern forming method suitable for forming fine patterns of large-scale integrated circuits.

[Prior Art] Recently, in semiconductor devices such as LSI and VLSI, 1
Chips containing several hundred thousand to several hundred and five semiconductor elements are emerging, and therefore there is a demand for miniaturization of element patterns formed on semiconductor substrates.

In order to meet this demand for miniaturization, conventional wavelengths of 436 nm (G line) or 3
Instead of the 65 nm (I-line) ultraviolet light, an excimer laser beam that can output ultraviolet light having a wavelength shorter than the G-line and I-line has been proposed.

For example, the excimer laser oscillator used in the light source of the excimer laser stepper disclosed in Japanese Patent Application Laid-Open No. 60-257521 has a 249n
It emits ultraviolet light with an extremely short wavelength.

This excimer laser light has excellent monochromaticity, directivity, and short pulse properties, and has high output, so it has extremely desirable performance as a light source for lithography. Further, since the resolution improves as the wavelength becomes shorter, it is expected that a resist pattern with high resolution can be formed by using this excimer laser light.

[Problems to be Solved by the Invention] However, forming a pattern using excimer laser light has the following problems.

In other words, since the wavelength of excimer laser light is extremely short, when a positive resist film made of phenol novolac material, which is commonly used in the past, is exposed to excimer laser light, the excimer laser light is strongly absorbed by this positive resist film, and the exposure Light is attenuated within the resist film.

For this reason, as shown in FIG. 2, after coating a positive resist film on the Si substrate 1, an excimer laser beam is applied.

When a positive resist pattern 10 is formed by selectively exposing the resist film to light, this resist pattern 10
The side walls of the SL substrate 1 are strongly inclined with respect to the surface of the SL substrate 1. In other words, the cross-sectional shape of the resist pattern 10 becomes close to a trapezoid. Therefore, this resist pattern 10 has poor dimensional reproducibility.

In addition, in a positive resist film made of an acrylic material such as polymethyl methacrylate (PMMA), there is almost no absorption of exposure light within the resist film as described above, and the cross-sectional shape of the resist pattern is approximately Although it is rectangular, the exposure sensitivity is approximately 1/10 that of phenol novolak resist.
0', and the heat resistance and plasma etching resistance are also extremely low, making it impractical.

The present invention has been made in view of such problems, and includes:
Using excimer laser light with extremely excellent spatial resolution, it is possible to form a resist pattern whose sidewalls are steep with respect to the substrate surface and with excellent dimensional reproducibility, thus making it possible to miniaturize the pattern of semiconductor devices. The purpose is to provide an effective pattern forming method.

[Means for Solving the Problems] The pattern forming method according to the present invention includes a step of applying a positive photoresist film containing a phenol novolac resin as a main component on a semiconductor substrate, and a step of applying a fluorescent material on the photoresist film. a step of depositing a thin layer of an organic material containing . and a step of selectively removing the exposed portion of the resist film.

[Function] In the present invention, after forming a positive photoresist film mainly composed of a phenolic novolak resin suitable for device manufacturing, a thin layer of an organic material containing a fluorescent material is deposited on the photoresist film, Next, the resist film is selectively exposed to excimer laser light through this thin layer.

By this method, 249n+ from the excimer laser light source
While the ultraviolet light having a wavelength of
The ultraviolet light has a wavelength distribution of nm.

This reduces absorption of excimer laser light in the resist film. Therefore, the sidewalls of the resist pattern obtained by removing the exposed area become steep with respect to the substrate, improving dimensional stability, and making full use of the excellent spatial resolution of excimer laser light to form fine resist patterns. It becomes possible to form.

[Example] Next, an example of the present invention will be described in detail with reference to the accompanying drawings.

First, as shown in FIG. 1(a), on a semiconductor substrate 1,
For example, a commonly used phenol novolac resin-based diagonal resist material is coated with
．． Apply to a thickness of OJ, tm.

Thereafter, for example, heat treatment is performed for 50 seconds on a 95° C. hot plate to form a positive resist film 2 having a thickness of 1.0 μm.

Next, as shown in FIG. 1(b), an aqueous solution of a mixture of fine powder of calcium tungstate (CaWO4), which is a fluorescent substance, and casein, a milk protein, is coated with a solution of, for example, 0.32 μm by a spin code method. Apply to a thickness of 80
Heat treatment for 2 minutes and 30 seconds on a hot plate at 0°C.
．． A fluorescent film 3 (thin layer) with a thickness of 30 μm is formed. In this case, the coating liquid for the fluorescent film 3 is 10.2% by weight.
A liquid mixture containing casein, 1.8% by weight of fine powder of calcium tungstate, and 88.0% by weight of pure water is preferred.

Next, as shown in FIG. 1C, the semiconductor substrate 1 is irradiated with ultraviolet light having a wavelength of 249 nm (indicated by arrows in the figure) from an excimer laser light source to form regions 4, 5, . . . on the substrate 1.
6 is selectively exposed to this short wavelength ultraviolet light (excimer laser light).

In this case, the ultraviolet light with a wavelength of 249 nm causes a fluorescent reaction within the fluorescent film 3 and is converted into ultraviolet light with a relatively long wavelength of 360 to 440 tv. In this way, the ultraviolet light that has passed through the fluorescent film 3 and shifted to the longer wavelength side enters the positive resist film 2 as it is.

Thereafter, as shown in FIG. 1(d), the semiconductor substrate 1 is immersed in pure water at a temperature of 40° C. for 60 seconds to remove the fluorescent film 3. Finally, the substrate 1 is immersed in an aqueous solution of tetramethylammonium hydroxide having a concentration of 2.38% to remove the positive resist film 2 in the exposed areas 4 and 5.6, thereby creating a resist pattern 2a. , 2b, 2c are formed.

In the pattern forming method configured as described above, ultraviolet light (excimer laser light) with a short wavelength of 249 nm is used.
While passing through the fluorescent film 3 on the resist film 2, the light is converted into ultraviolet light having a relatively long wavelength with a wavelength distribution of 400±40 nm, and enters the resist film 2. For this reason, 24
Compared to the case where ultraviolet light with a short wavelength of 9 nm is directly incident into the resist film 2, the absorption of ultraviolet light within the resist film 2 is reduced, and the H-line (wavelength: 404 nm), which is commonly used in the past, is reduced. absorption in ultraviolet light.

Therefore, the side walls of the resist patterns 2a, 2b, and 2c rise steeply relative to the substrate surface, and the cross-sectional shape of the resist patterns 2a, 2b, and 2c is not trapezoidal but exhibits extremely good rectangularity, as in the case of the conventional H-line. For this reason, resist patterns 2a, 2b
, 2c has extremely high dimensional reproducibility, and since excimer laser light has a short wavelength (249nu), the spatial resolution of the excimer laser light optical system is H-line (404na+)
It is significantly superior to the G line (436 nm) and can easily form a pattern of about 0.4 to 0.5 μm.

[Effects of the Invention] As explained above, according to the present invention, it is possible to form a resist pattern whose sidewalls rise steeply at an angle nearly perpendicular to the surface of the substrate or the underlying layer, and which has an extremely rectangular cross-section. It is possible to obtain an excellent resist pattern. Therefore, the dimensional reproducibility of the pattern is stabilized, and it is possible to form a resist pattern that is significantly finer than in the conventional case. Therefore, the present invention contributes to higher integration and improved performance of semiconductor devices, and has great effects.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are cross-sectional views showing an embodiment of the present invention in the order of steps, and FIG. 2 is a cross-sectional view showing the shape of a pattern formed by a conventional method. 1: Semiconductor substrate, 2: Phenol novolac positive resist film, 2a, 2b, 2c, 10: Resist pattern, 3: Fluorescent film, 4, 5, 6: Eximer laser light exposure area

Claims (1)

[Claims] A process of applying a positive photoresist film mainly composed of phenol novolac resin on a semiconductor substrate, a process of depositing a thin layer of an organic material containing a fluorescent material on the photoresist film, and a process of applying a thin layer of an organic material containing a fluorescent material to the photoresist film. selectively exposing the resist film to excimer laser light; completely removing the thin layer through a predetermined development process;
A pattern forming method comprising the step of selectively removing an exposed portion of the resist film.