JPH08181050A - Removing method for resist and cleaning method for board - Google Patents

Abstract

PURPOSE: To extremely simplify steps, to remove a fear of board damage and to remarkably facilitate a waste liquid treatment by dipping the board with adhered resist in supercritical fluid for a predetermined time. CONSTITUTION: First, an exposed board 3 is placed on a reticular holder 2. Then, a high-pressure vessel 1 is introduced from an inlet with high-pressure carbon dioxide in the state that the vessel 1 is held at a temperature of a critical temperature or lower. In this case, the carbon dioxide exists separately to a liquid layer part 5 and a gas layer part 6, but the board 3 is not dipped in the part 5. Thereafter, the vessel 1 is maintained in this state for about 5min, and thereafter, the temperature of the vessel is lowered to the critical temperature or lower. Thus, the steps are extremely simplified, a fear of board damage is removed, and waste liquid treatment is remarkably facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies, for example, a fine pattern processing to various device substrates, photomask substrates, X-ray mask substrates and the like used in semiconductors and their peripheral fields by applying a lithography method. In some cases,
The present invention relates to a resist removing method for removing used resist from these substrates and a substrate cleaning method for removing foreign matters adhering to these substrates.

[0002]

2. Description of the Related Art Generally, a so-called lithographic method for forming a fine pattern generally comprises applying a resist to a surface of a substrate to be processed to form a resist film, exposing the resist film to a desired pattern, and thereafter exposing the resist film to a desired pattern. The exposed substrate is developed to remove a part of the resist along the pattern to form a resist pattern, and then etching and other processes are performed from the side where the resist pattern is formed. The substrate is processed according to the pattern by performing a treatment, and then the used resist is removed and the substrate is washed.

In the above process, the resist pattern formed on the substrate by the developing process is used by etching the substrate and other processing, and the resist is used to remove the used resist. As the removal (peeling) method, various methods as described below have been tried.

A method of decomposing and removing a used resist by using a solution having a strong oxidizing action, for example, a solution in which hydrogen peroxide is mixed with hot concentrated sulfuric acid, an organic solvent, for example, resist stripping manufactured by Tokyo Ohka Kogyo Co., Ltd. A method of peeling using the agent J100 (trade name), a method of ashing and removing the resist by an oxygen plasma method.

Further, the substrate from which the used resist has been removed is subjected to a cleaning step, and conventionally, the following method has been tried for this cleaning step.

A. The substrate is immersed in DI water (ultra pure water) and ultrasonically cleaned, and then IPA (isopropyl alcohol)
A method of immersing in water and ultrasonically cleaning the same, and then drying with IPA or Freon vapor; b. Brushes and sponges that rotate on the surface of the substrate on which the used resist has been formed, while continuously moving the substrate surface while spraying DI water or a mixture of DI water and a surfactant (eg, RBS). Alternatively, a method of contacting and removing a cloth or the like, c. A method of peeling and removing the resist by the expansive force of the gas that has penetrated into the resist by bringing the substrate into contact with a liquefied gas or a supercritical gas and then expanding this gas (for example, see JP-A-60-192333) .

[0007]

However, the above-mentioned resist removing method has the following drawbacks.

That is, the method of using a strong oxidizing solvent among the above resist removing methods is limited in its application range because the solvent used may act on the substrate which is the base of the resist and damage it. In particular, for example, when the substrate is a liquid crystal panel substrate having an ITO film (a transparent electrode film made of indium oxide containing tin) formed on its surface, the solvent damages the ITO film. Could not be applied.

Further, in the method using the above organic solvent, it is usually necessary to heat the organic solvent in order to enhance the elution effect, and it is difficult to take safety into consideration, and at the same time, the type of resist and process conditions are required. Depending on the
In some cases, the organic solvent cannot completely remove the used resist.

The above-mentioned methods (1) and (2) also have a problem of waste liquid treatment.

Further, although the above-mentioned method using oxygen plasma is excellent in the resist removing effect, it has a drawback that the apparatus becomes large in size, the equipment cost is increased, and the substrate may be contaminated with metal. .

Of the above-mentioned conventional cleaning methods, the ultrasonic cleaning using DI water or the like in (a) above is actually prepared by separately preparing DI water or IPA aqueous solution in a plurality of tanks, Ultrasonic cleaning is performed by successively immersing in each of these tanks, the number of steps is large and the processing is complicated, and the substrate may be damaged by ultrasonic waves.
In particular, for example, in a multi-layered film substrate having a plurality of thin films laminated on the surface, a weak film inside may be intensively damaged.

The method (b) of mechanically peeling off with a brush or the like is effective for a strong glass substrate or an unprocessed wafer, but is a multilayer having a soft thin film layer inside. It could not be applied to a film substrate or a substrate such as a thinned X-ray mask because of its mechanical strength. In addition, these
Both the methods (a) and (b) have a problem of waste liquid treatment.

Further, the method (c) of utilizing the expansive force of gas or the like does not have the problems of the above (a) and (b), but the substrate is housed in a high-pressure container and its internal pressure is rapidly increased. Since the impact may damage the substrate, it is not applicable to thin film X-ray masks with weak mechanical strength or multilayer film substrates having a soft thin film layer inside. It was

The present invention has been made under the above-mentioned circumstances, and the method of removing a resist and the method of cleaning a substrate can greatly simplify the process, eliminate the risk of substrate damage, and significantly facilitate waste liquid treatment. The purpose is to provide.

[0016]

DISCLOSURE OF THE INVENTION The present invention discovers a novel fact that when a substrate having a resist attached thereto is immersed in a supercritical fluid for a certain period of time, the resist removing action and the substrate washing action are obtained. And has the following respective configurations.

(1) A method of removing a resist, which is used for pattern formation in a process of forming a fine pattern by applying a lithographic method, to remove a resist made of a used polymer compound remaining after being used for pattern formation. In the method of removing a resist, the resist is removed by immersing at least a portion of the substrate to which the resist is attached in a supercritical fluid.

(2) A method of removing a resist, characterized in that the cleaning is performed by immersing the substrate in a supercritical fluid in a method of cleaning a substrate on which a fine pattern is formed by a lithography method.

[0019]

In the above structure (1), at least a portion of the substrate to which the resist is attached is immersed in the supercritical fluid for a certain period of time, so that the resist is eluted into the supercritical fluid. It has been confirmed that the resist is removed.

Further, in the constitution (2), it has been confirmed that foreign matter other than the resist can be neatly removed by immersing the substrate in the supercritical fluid.

The term "supercritical fluid" as used herein means, in a broad sense, a state in which it is not liquefied even if it is compressed to a high density, that is, a generic term for gases heated to a critical temperature peculiar to the substance or more, and it is an almost ideal gas. Although it also includes a low density state showing properties close to, a supercritical fluid in the present invention is a state in which it is compressed to a high density by being placed under a pressure significantly higher than normal pressure (for example, several tens of atmospheres), For example, in a conspicuous case, it means a supercritical fluid in a narrow sense in a highly compressed state close to or higher than the density of a liquid.

That is, when the density is increased in this way, its microscopic structure gradually becomes similar to that in the liquid state (confirmed by the measurement of X-ray and neutron diffraction), while the ordinary liquid It has a unique property that the kinematic viscosity is significantly smaller than that of water (for example, water) and the diffusion coefficient is significantly large (for a supercritical fluid, for example,
"Chemistry and Industry" Volume 40. 1987. (See page 753).

According to the consideration of the inventors, in such a high-density supercritical fluid, while the molecules are compressed to a high density close to or higher than a liquid, the movement of each molecule is extremely active. Therefore, it is considered that the individual molecules easily permeate and elute even those which cannot permeate in the normal liquid state.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) In this embodiment, a used resist of an X-ray mask on which a resist pattern is formed is removed,
It is also an example of cleaning the substrate. In this embodiment, the development for forming the resist pattern is also performed using a supercritical fluid.

First, an X-ray mask blank is manufactured as follows.

Si was formed on the surface of a disk-shaped silicon wafer (thickness: 400 μm) with a diameter of 3 inches by reactive sputtering.
A thin film of N 2 (thickness: 2 μm) is formed, etching is performed from the back surface of this wafer to remove the central part of the 400 μm thick wafer, leaving a supporting frame part on a thick ring around the central part. As a thin silicon wafer having a thickness of 2 μm. Then, a tantalum thin film (thickness;
0.6 μm) to obtain a blank for X-ray mask.

Next, the photoresist AZ1 hard-baked at 200 ° C. was formed on the surface of the X-ray mask blank.
Film of 350J (trade name of Hoechst) (thickness: 2.5 μ
m), a SiO ₂ film (thickness: 1000 Å) is formed on this film, and finally, the above is formed by spin coating.
An electron beam resist PMMA film (thickness: 3000 angstrom) is formed on the SiO ₂ film.

FIG. 4 is a cross-sectional view of the X-ray mask blank thus obtained, in which reference numeral 11 is a support frame portion and 1 is a support frame portion.
2 is a thinned silicon wafer, 13 is a tantalum film, 14 is a photoresist film, 15 is a SiO ₂ film, and 16 is a PMMA film.

Next, the blank electron beam resist PMMA for the X-ray mask is exposed by an electron beam drawing apparatus. At this time, the accelerating voltage of the electron beam is 20 KV and the dose is 60 μc / c.
m ² , the minimum dimension of a figure consisting of lines and spaces is 0.5
μm.

Next, the exposed silicon wafer is immersed in a supercritical fluid for development. In this case, carbon dioxide (CO ₂ , critical temperature 31 ° C, critical pressure 72.8 atm, critical density 0.55 g / cm ³ ) was used as the supercritical fluid, and 0.5% by weight of methyl isobutyl ketone (MiBK) was used as the supercritical fluid. Used by adding.

FIG. 1 to FIG. 3 are views showing the situation of this developing process.

In the figure, reference numeral 1 is a high-pressure container, and a net-shaped holder 2 is provided in the high-pressure container 1 at substantially the center thereof.

When developing, first, the exposed substrate 3
Is placed on the net-shaped holder 2. At that time, the exposed resist 4 formed on the substrate 3 faces downward in the drawing. In addition,
Depending on the case, it may be placed upside down.

Next, high-pressure carbon dioxide is introduced from an inlet (not shown) while the high-pressure vessel 1 is kept at a temperature below the critical temperature. The amount of introduction is such that the density becomes 0.55 g / cm ³ when carbon dioxide becomes a supercritical fluid in the high pressure vessel 1. As shown in FIG. 1, the introduced carbon dioxide exists separately in the liquid layer portion 5 and the gas layer portion (vapor portion) 6, but the substrate 3 is not present in the liquid layer portion 5. It is not soaked.

Next, the temperature of the high pressure vessel 1 is raised to 45 ° C. by a temperature control means (not shown). As a result, as shown in FIG. 2, the carbon dioxide in the high-pressure vessel 1 becomes the supercritical fluid 7
Becomes

This state is maintained for 5 minutes, and then the temperature of the high pressure vessel is lowered to the critical temperature or lower.

As a result, a concavo-convex pattern can be formed on the PMMA resist, in which case the depth of the pattern is 3000 angstrom by the stylus type step gauge, and further, the SiO ₂ film is formed in the concave part. It was confirmed that it was completely exposed.

Next, the PMMA electron beam resist 1 is thus obtained.
Reactive ion etching (RIE) is performed on the resist pattern formed in FIG.
_{2 The} above-mentioned resist pattern is transferred to the film 15, and then the PMMA resist film 16 and Si on which these patterns are formed are formed.
RIE using oxygen gas is performed on the O ₂ film 15 to form this pattern in the photoresist AZ1350J film 14
Transfer to. Then, this photoresist AZ135
RIE using CL ₂ gas is performed on the 0J film 14 and X
By etching the tantalum film 13 which is a line absorber, the tantalum film 13 formed on the silicon thin film 12 is etched.
Can form a desired pattern. FIG. 5 is a sectional view showing the substrate thus obtained.

By the way, on the tantalum film 13, a used resist (AZ1350J) 14a having a thickness of about 1.5 μm is formed.
Remains.

Then, next, the used resist 14a is used.
The substrate on which is remaining is immersed in a supercritical fluid to remove the resist and wash the substrate.

When the resist is removed and the substrate is washed, the substrate on which the used resist 14a remains remains as shown in FIG.
Placed on the reticulated holding body 2 of the high-pressure container 1 shown in Fig. 2, the density of the supercritical fluid in the high-pressure container 1 becomes 0.55 g /
Carbon dioxide in an amount of cm ³ and Mi in an amount of 7% by weight
Introduce BK and maintain the high pressure vessel at 45 ° C. for 45 minutes.
As a result, the used resist is removed and the substrate is washed.

As a result of observing the substrate from which the used resist has been removed and washed as described above with naked eyes under oblique illumination with a condenser lamp and with a 50 times magnified observation under an optical microscope, residual resist and other foreign matter are found. Not observed at all, it has an extremely clean surface condition and the above-mentioned 2 μm thick Si
It has been confirmed that the N film is not damaged at all.

(Embodiment 2) In this embodiment, as a substrate, an electroluminescence (EL) panel in which a thin film of eight layers is laminated on the surface is used, and a photoresist AZ1350J is used as the uppermost AL film. This is an example of the case where a wiring pattern is formed by using the wiring pattern and the used resist remaining on the wiring pattern is removed and washed.

The substrate on which the used resist remains is placed on the net-shaped holder 2 of the high-pressure container 1 shown in FIG. 1, and the density of the supercritical fluid in the high-pressure container 1 is changed. Carbon dioxide in an amount of 0.50 g / cm ³ and MiBK in an amount of 5% by weight are introduced, and the high-pressure container is maintained at 45 ° C. for 30 minutes. As a result, the used resist is removed and washed.

As a result of observing the substrate from which the used resist has been removed and washed as described above with naked eyes by oblique illumination with a condensing lamp and with a magnification of 50 times with an optical microscope, residual resist and other foreign matter are found. It was confirmed that the surface layer was not observed at all, and the surface state was extremely clean, and that the inner layer was not broken at all in the operation test of the EL panel.

According to the above-described embodiments, a solvent having a strong oxidizing action is used, or mechanical vibration (when the ultrasonic waves are used) or impact force (expansion force of the gas is used) on the entire substrate. In some cases, the supercritical fluid molecule does not need to be applied and exerts the necessary action only on the resist that the supercritical fluid molecules directly contact to perform development, removal, or cleaning, so development is performed without damaging the underlying substrate or thin film. , Can be removed or washed.

Further, the fluid to be used is an inert gas, or one obtained by adding an extremely small amount of an organic solvent thereto, and is only immersed in these for a certain period of time, so that the process is extremely simple and the waste liquid treatment is carried out. The post-treatments such as the above have the advantage that they are significantly easier than the conventional ones.

In the above examples, carbon dioxide was used as the supercritical fluid and a slight amount of an organic solvent was added to the carbon dioxide to significantly shorten the treatment time. However, it is necessary to shorten the treatment time. If it is not necessary, it is not necessary to add an organic solvent, and the supercritical fluid is not limited to carbon dioxide, and other inert gases such as Ar, Kr, and Xe may be used. Although it is somewhat inferior in safety against fire, etc., for example, lower hydrocarbons such as CH ₄ ,
Freons such as CF ₃ H can also be used.

Further, in each of the above-mentioned embodiments, an example in which a photoresist is used as the resist is shown, but this may be an electron beam resist such as PMMA or another organic polymer film such as polyimide. .

[0050]

As described in detail above, according to the present invention, development or removal of the resist is carried out by immersing the exposed substrate or the substrate with the resist attached thereto in a supercritical fluid for a certain period of time. Thus, this has an excellent effect that the process is extremely simplified, the risk of substrate damage is eliminated, and the waste liquid treatment is significantly facilitated.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a resist removing method and a substrate cleaning method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a resist removing method and a substrate cleaning method according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a resist removing method and a substrate cleaning method according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing an X-ray mask blank.

FIG. 5 is a cross-sectional view showing an X-ray mask with a used resist attached thereto.

[Explanation of symbols]

1 ... High-pressure container, 3 ... Exposed substrate, 4 ... Exposed resist, 7 ... Supercritical fluid, 14a ... Used resist.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazudo Nakagawa 1-32 Nishimachi, Kokubunji-shi, Tokyo No. 254 National Housing (72) Inventor Yoichi Yamaguchi 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Hoya shares In the company

Claims (2)

[Claims] 1. A method for removing a resist, which removes a used polymer compound resist applied after being applied to a substrate surface and used for pattern formation in the process of forming a fine pattern by applying a lithography method. The resist removing method is characterized in that the resist is removed by immersing at least a portion of the substrate to which the resist is attached in a supercritical fluid. 2. A method of removing a substrate, which comprises cleaning a substrate having a fine pattern formed by a lithographic method, wherein the cleaning is performed by immersing the substrate in a supercritical fluid.