JPH04155914A - X-ray exposure - Google Patents

Abstract

PURPOSE:To control the size of a pattern easily and to increase the survival rate of a film by a method wherein the high-energy light is applied to a resist layer in an oxygen atmosphere to form a hardly-soluble layer and then the X-rays are applied to the resist through a mask in an atmosphere having no oxygen. CONSTITUTION:Before X-ray exposure, high-energy light such as KrF excimer laser light is applied to a resist layer 13 which is deposited on a semiconductor substrate 2 in an oxygen atmosphere. Ozone is generated in this process and a hardly-soluble layer 15 is formed on the surface of the resist layer 13 due to the ozone. As the next step, with the semiconductor substrate positioned for exposure on an X-ray aligner, an atmosphere between the semiconductor and a mask is replaced with an atmosphere having no oxygen and gap and in-plane alightments are conducted between the mask and semiconductor substrate (the resist layer). Then, X-rays 7 are applied to on the resist layer 13 through the mask 4 for exposure. The resist layer 13 irradiated with X-rays partly includes a hardly-soluble layer 15 and is brought into such a condition that it may be dissolved by development. With the hardly-soluble layer 15 being left over on the surface of a part of the resist layer 13 which has not been irradiated with the X-rays, a resist pattern 18 of the non-exposed part remains, retaining its shape.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an X-ray exposure method using a resist whose film thickness is reduced by dissolving the unexposed areas when developed. This is an X-ray exposure method in which a resist coated on a substrate is exposed to X-rays, and the resist is irradiated with high-energy light in an oxygen-containing atmosphere. and then irradiating the resist with X-rays through a mask in an oxygen-containing atmosphere.

[Industrial Application Field] The present invention relates to an X-ray exposure method, and more particularly to an X-ray exposure method using a resist whose film thickness decreases by dissolving unexposed areas when developed.

In recent years, with the increasing density of semiconductor devices such as memory devices, there has been a demand for smaller patterns, and pattern widths have become submicron,
progressing to quarter microns.

In order to realize such thin patterns, we are developing X-ray phosphorography technology that is highly mass-producible, especially X-ray phosphorography technology using SOR light.
Line phosphorography technology is being developed.

In this specification, unless otherwise specified, X-rays refer to electromagnetic waves with energy corresponding to the energy level of core electrons with respect to vacuum level, and high-energy light refers to ultraviolet light, especially far-field light excluding vacuum ultraviolet light. Refers to ultraviolet light and near ultraviolet light.

[Prior Art] In many resists used for X-ray exposure, unexposed areas also dissolve when developed. For example, Hitachi Chemical product name R
E-5000P, Z-CMR manufactured by Nippon Zeon, PMMA manufactured by Tokyo Ohka, 0EBR-1000, etc., have a low residual film rate after development because the dissolution rate of the unexposed area is fast. If such a resist is used alone, it is difficult to control the resist pattern size due to side etching in unexposed areas, and the low residual film rate makes it difficult to obtain a sufficient selectivity when etching semiconductor materials. .

Therefore, a method is used in which a self-developing type poorly soluble layer that is developed by exposure to light is coated on the X-ray resist and then developed. In the exposed area, the poorly soluble layer begins to dissolve with force,
In the unexposed area, the hardly soluble layer acts as a protective film. Furthermore, during development, the unexposed area is kept from coming into contact with the developer as much as possible in order to improve the residual film rate.

However, this method requires complicated work steps and increases the probability of defects occurring.

[Problems to be solved by the invention] In order to form a pattern with little deterioration and obtain a good element turn, it is necessary to control the turn size after development, improve the residual film rate, and improve the etching process during etching. It is desirable to obtain the necessary selectivity.

An object of the present invention is to provide an X-ray exposure method that allows easy control of pattern size and improves film remaining rate.

[Means for Solving the Problems] The X-ray exposure method of the present invention is an X-ray exposure method in which a resist coated on a substrate is exposed to X-rays, and the resist is exposed to high-energy light in an oxygen-containing atmosphere. and then irradiating the resist with X-rays through a mask in an oxygen-free atmosphere.

[Function] When a resist is irradiated with high-energy light in an oxygen-containing atmosphere, the resist becomes less soluble on the surface of the resist.

After that, X-rays are irradiated to the resist through a mask in an oxygen-free atmosphere, and X-ray pattern exposure is performed.
The resist where the radiation is irradiated becomes easily dissolved. In the areas not irradiated with X-rays, the previously formed poorly soluble layer remains. By performing development while utilizing this poorly soluble layer as a protective layer, it is possible to maintain accuracy in pattern size and to improve the rate of film remaining after development.

In this way, a resist pattern with a high residual film rate after development and little deterioration can be obtained.

[Example] Hereinafter, the present invention will be explained along with examples.

FIG. 1 schematically shows an X-ray exposure apparatus.

SOR light 7 emitted from an SOR light source (not shown) is reflected by a mirror 6 provided within the optical vacuum region, and short wavelength components are cut off. The mirror 6 is made of, for example, Pt,
It is formed from quartz, etc.

The SOR light with short wavelength components cut is in the high vacuum region and He
For example, a Be window 5 with a thickness of about 20 μm separates it from the atmosphere.
The long wavelength components are cut off by passing through the Be window 5. The SOR light 7 passing through the Be window 5 becomes He
The light passes through the atmosphere and is emitted from an exit window 8 formed of a SiC film, a Kapton film, or the like. Note that the He atmosphere is surrounded by the He gas container 3. The SOR light transmitted through the emission window 8 is irradiated onto the semiconductor substrate 2 through the mask 4. The mask 4 has an opening in the center of the silicon wafer, for example, and a film of an X-ray transparent material such as SiC is formed there, and Ta, which is an X-ray absorber, is formed on the transparent film.
A pattern of heavy metal such as gold or W is formed. Incident X-rays (S.

R light) is transmitted only through the portion without the absorber. A resist layer is formed on the semiconductor substrate 2.

The resist layer is selectively exposed to X-rays transmitted through the mask 4.

Prior to exposure to X-rays, the resist layer coated on the semiconductor substrate 2 is irradiated with high-energy light such as KrF excimer laser light. When irradiating the excimer laser light at a location other than the X-ray exposure device, the entire surface of the semiconductor substrate 2 may be irradiated with the excimer laser light in an oxygen-containing atmosphere such as the atmosphere.

When irradiating excimer laser light in an X-ray exposure device, the excimer laser light is guided to the same optical path as X-rays, and the resist layer is irradiated with the mask 4 removed or through the mask 4 in an atmosphere containing oxygen. do it. When excimer laser light is irradiated into an atmosphere containing oxygen, ozone is generated.
A hardly soluble layer is formed on the resist surface due to the influence of ozone. This hardly soluble layer has a property that it is difficult to dissolve in a developer compared to the original resist.

Thereafter, the surroundings of the semiconductor substrate 2 are replaced with an oxygen-free atmosphere, and the resist layer on the semiconductor substrate 2 is pattern-exposed with X-rays (SOR light) 7.

The area irradiated with X-rays in an oxygen-free atmosphere changes so that it dissolves when developed. A hardly soluble layer remains in areas that were not exposed to X-rays.

In this way, the residual film rate after development can be improved by once exposing the resist layer to light in an oxygen-containing atmosphere to form a hardly soluble layer, and then exposing it to X-rays in an oxygen-free atmosphere. can.

Note that if the X-ray exposure is also performed in an atmosphere containing oxygen such as the air, a hardly soluble layer will be formed on the surface during the X-ray exposure, and selectivity will be lost. Furthermore, even if an oxygen barrier film is applied to the resist or pre-exposure is performed using excimer laser light in an oxygen-free atmosphere, there is no change in the dissolution rate between the unexposed and exposed areas, and the residual film rate is improved. does not contribute to

Note that the semiconductor substrate 2 is fixed on the stage 1 by a wafer chuck or the like, and its position is changed by driving the stage 1. In the figure, 11 indicates a stage drive system. Further, the optical alignment system 9.10 adjusts the alignment between the mask 4 and the semiconductor substrate 2 in the in-plane direction and the out-of-plane direction, for example.

Hereinafter, an X-ray exposure method according to an embodiment of the present invention will be described in more detail with reference to FIGS. 2(A) to 2(F).

First, as shown in FIG. 2(A), a semiconductor substrate 2 made of silicon or the like is prepared.

Next, as shown in FIG. 2(B), a resist layer 13 is applied onto the surface of the semiconductor substrate 2 using a spinner or the like. The resist layer 13 is formed of a resist layer with a thickness of about 1 μm, such as RE-5000P manufactured by Hitachi Chemical, which can be used for X-ray exposure.

As shown in FIG. 2(C), the entire surface of the resist layer 13 on the semiconductor substrate 2 is covered with an excimer laser beam in an atmosphere of 1 atm.
Irradiate at 4.

Note that an atmosphere containing oxygen may be used instead of the atmosphere.

However, oxygen with a concentration of 1% or less is not included in the oxygen-containing atmosphere. For example, a KrF laser can be used as the excimer laser. Other excimer lasers (eg, ArF) or other high-energy light sources that generate high-energy light in the ultraviolet region can also be used.

When high-energy light is irradiated into an oxygen-containing atmosphere, a chemical reaction occurs and ozone is produced. At this time, the resist is also exposed to high-energy light, but if ozone is present during the photosensitive reaction, the resist becomes less soluble due to the influence of ozone. This excimer laser irradiation step may be performed within the X-ray exposure apparatus or outside the X-ray exposure apparatus. Further, when performing the irradiation in an X11A exposure apparatus, it is preferable to irradiate the entire surface of the semiconductor substrate 2 with the mask 4 removed from the viewpoint of intensity, but irradiation may be performed through the mask. When high-energy light is irradiated through a mask, the entire surface of the resist layer is not irradiated, but if the pattern width is as narrow as submicron or less, the influence of the irradiated area extends to non-irradiated areas due to diffusion after irradiation. It is possible to obtain the same effect as full-surface irradiation.

The state of the resist layer 13 with the hardly soluble layer 15 formed in this way is shown in an enlarged manner in FIG. 2(A).

The hardly soluble layer 15 is formed, for example, to a thickness of about 0.1 μm on the surface of a resist having a thickness of about 1 μm.

Next, with the semiconductor substrate placed at the exposure position of the X-ray exposure apparatus, the atmosphere between the semiconductor substrate and the mask is replaced with an oxygen-free atmosphere. That is, the resist layer is brought into contact with an atmosphere that does not contain oxygen. Also, the gap and in-plane alignment between the mask and the semiconductor substrate (resist layer) are performed.

As shown in FIG. 2(E), the resist layer 13 is irradiated with X-rays 7 through the mask 4 for exposure.

The X-rays are, for example, X-rays with a wavelength of about 4 to 20λ. The mask 4 includes a pattern 1 of an X-ray absorber such as Ta on a membrane 16 made of SiC or the like and having a thickness of about 2 μm.
7 was formed.

The width of the pattern is, for example, about 0.1 μm for a thin pattern and about 10 μm for a thick pattern. X irradiated on membrane 16
The line passes through the membrane 16 as it is and passes through the resist layer 1.
Irradiate to 3. The X-rays irradiated onto the absorber 17 are reflected and absorbed there, and the resist layer 13 is not irradiated. In this way, resist layer 13 is selectively exposed according to mask 4.

The resist layer 13 irradiated with X-rays becomes the hardly soluble layer 1
Including the part 5, it changes to a state where it dissolves by development. In areas not irradiated with X-rays, the hardly soluble layer 15 remains on the surface and is prevented from dissolving even if developed using a developer.

When the development is performed, the unexposed portions of the resist pattern 18 remain without deformation, as shown in FIG. 2(F).

Although we have described the case where the surface of the resist layer is irradiated with excimer laser light before X-ray exposure to form a hardly soluble layer, other high-energy light having a wavelength in the ultraviolet region may also be used instead of excimer laser light. can.

In addition, although we have described the case where the entire surface of the resist layer is irradiated with excimer laser light without a mask, if the width of the absorber of the mask is narrow, for example, about 1 micron or less,
High energy light may be irradiated through the mask. Although the high-energy light is blocked by the absorber on the mask and the resist layer is selectively exposed, the influence of exposure to high-energy light also spreads in the plane of the resist layer due to diffusion.

For this reason, the resist layer that is exposed leaving a narrow area is also
A hardly soluble layer is formed on the entire surface of the resist layer, which is equivalent to the entire surface of the exposed resist layer.

Although a case has been described in which He is used as the oxygen-free atmosphere, other inert gases such as Ar, N2, etc. may also be used.

Although the present invention has been described above with reference to Examples, the present invention is not limited thereto. For example, it will be obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

[Effects of the Invention] As explained above, according to the present invention, since a hardly soluble layer is formed by irradiating the resist layer with high-energy light in an oxygen-containing atmosphere, the residual rate is low in development after X-ray exposure. is reduced, pattern deterioration can be prevented, and the remaining film rate can be improved.

The accuracy of the resulting pattern is improved, and the etching selectivity is also improved.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an outline of the X-ray exposure apparatus, and Figure 2 (
A) to (F) are cross-sectional views for explaining an X-ray exposure method according to an embodiment of the present invention. In the figure, 2 semiconductor substrate 3 He gas container 4 mask 5 Be window 7 SOR light (X-ray) 8 exit window (SiC film) 13 resist layer 14 excimer laser light 15 hardly soluble layer 16 mask membrane 17 mask absorber 18 Resist pattern\-21 (A) Si substrate 13 Resist layer (B) Resist layer coating 14: Excimer laser light (C) Excimer laser light irradiation 15: Hardly soluble layer (D> Enlarged image *Example Fig. 2 ]) 17: Absorber (E) pattern exposure/18 Resist pattern (F) phenomenon (resist pattern formation) Example Fig. 2 (Part 2)

Claims (2)

[Claims] (1), exposing the resist coated on the substrate to X-rays
A line exposure method, which includes a step of irradiating the resist with high-energy light in an oxygen-containing atmosphere (Fig. 2 (C)), and then a step of irradiating the resist with X-rays through a mask in an oxygen-free atmosphere. (FIG. 2(E)). (2) The X-ray exposure method according to claim 1, wherein the high-energy light irradiation step is performed through the mask.