JPH0383065A - Method for forming pattern of resist, method for removing resist and method for washing substrate - Google Patents

Abstract

PURPOSE:To simplify stages by executing the processing of development by immersing the part, where a resist is formed, of an exposed substrate into a high-pressure liquid below the critical pressure. CONSTITUTION:The processing of the development is executed by immersing the part, where the resist 4 is formed, of the exposed substrate 3 into the high- pressure liquid 5 below the critical pressure. Namely, the part having a low mol.wt. or the part having a high elution rate is selectively eluted in the high- pressure liquid 5 when the part formed with the resist is immersed for a specified period of time in the high-pressure liquid 5 below the critical pressure. The development is executed and the pattern of the resist 4 is thus formed. The stages are simplified in this way.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention applies the lithography method to various device substrates, photomask substrates, and XR mask plates used in, for example, semiconductor and peripheral fields. When micropatterning is performed on these substrates, there are resist pattern forming methods for forming resist patterns on these substrates, resist removal methods for removing resist from these substrates, and substrate removal methods for removing foreign substances attached to these substrates. Regarding cleaning method.

[Prior Art] A fine pattern forming method using a so-called lithography method generally involves coating the surface of a substrate, which is a workpiece, with a resist to form a resist film, and then exposing the resist film to a desired pattern. A resist pattern is formed by developing the exposed substrate and removing a portion of the resist along the pattern, and then etching or other processing is performed from the side on which this resist pattern is formed. The process includes processing the substrate along the pattern, and then removing the used resist and cleaning the substrate.

Incidentally, in the above-mentioned procedure, the resist pattern forming method for forming the resist pattern is performed by the steps of exposure and development, but conventional exposure and development were performed as follows.

That is, first, exposure is performed by irradiating the resist (made of a polymer compound) with radiation such as electron beams, X-rays, or ultraviolet rays along a desired pattern. As a result of this radiation irradiation, the portions of the resist that have been irradiated with radiation and the portions that have not been irradiated have greatly different molecular weights or different structures. In other words, radiation irradiation causes a main chain scission reaction, resulting in a lower molecular weight (resists that undergo this type of reaction are called positive resists), or conversely, a crosslinking reaction occurs, resulting in a higher molecular weight, resulting in a lower molecular weight. (So-called negative resist), which causes a significant difference in molecular weight from the area that is not irradiated with radiation, or a novolac photoresist such as Hoechst's AZI: 350 (trade name). In addition, specific functional groups are generated by photochemical reactions in the radiation-irradiated area, resulting in a difference in elution rate with respect to the solvent between the radiation-irradiated area and the non-radiation-exposed area.

In short, the development treatment performed after this exposure treatment is based on the fact that the portions of the resist that have undergone the exposure treatment that have a low molecular weight are generally more easily eluted in ordinary solvents than the portions that have a high molecular weight. The difference in elution rate is utilized to selectively elute and remove the low molecular weight portion or the portion with a fast elution rate.

This development process actually includes, in addition to the original development, a rinsing and drying process that is carried out after this development, or a pretreatment process before development, and the rinsing process is also divided into two stages. Sometimes it is done. In addition, in this rinsing step, since a solvent consisting of a substance with a strong elution effect or a mixed solution of multiple substances is used during the development, these solvents may penetrate into the resist and cause the resist film to swell. In order to eliminate this risk, a relatively mild solvent or mixture is used to replace the strong solvent that has penetrated into the resist, and the resist is swollen. It tightens the resist.

In the actual manufacturing process, such processing of development, rinsing, and drying is usually carried out using the so-called spin spray method, in which the object to be processed, such as a silicon wafer substrate, is rotated, and a solvent is jetted from a spray nozzle onto the object. is used. That is, first, the strong solvent is ejected from the nozzle to perform a developing process, and then, overlapping this for several seconds, the mild solvent is ejected from the nozzle to perform a rinsing process. This is done by performing a drying process using a so-called spin dry method by rotating the substrate at high speed. This prevents the substrate such as the silicon wafer from being contaminated by the solvent as much as possible. In this case, in order to reduce contamination as much as possible, the solvents used in all steps are clean and contain very few contaminants and impurities.

In addition, the resist pattern formed on the substrate by the development process becomes used after being subjected to etching process or other processing on the substrate, but resist removal (stripping) is performed to remove this used resist. Conventionally, various methods have been tried as described below.

■ A method of decomposing and removing used resist using a solution with a strong oxidizing effect, such as a solution of hot concentrated sulfuric acid mixed with hydrogen peroxide; ■ An organic solvent, such as a resist stripper manufactured by Tokyo Ohka Kogyo Co., Ltd. A method of peeling using J100 (trade name); (2) A method of ashing and removing the resist using an oxygen plasma method.

Furthermore, the substrate from which the used resist has been removed is subjected to a cleaning process, and conventionally the following methods have been attempted for this cleaning process.

a. Immerse the substrate in DI water (ultra-pure water) and perform ultrasonic cleaning.
Next, the substrate surface on which the used resist is formed is immersed in IPA (isopropyl alcohol) water, subjected to ultrasonic cleaning, and then dried with IPA or Freon vapor. A method in which the surface of the substrate is continuously moved while spraying a surfactant (for example, RBS, etc.), and a rotating brush, sponge, cloth, etc. is brought into contact with the substrate to remove it, C1 liquefied gas or supercritical A method in which the resist is peeled off and removed by the expansion force of the gas that has penetrated into the resist by bringing a substrate into contact with a gas and then expanding the gas (see, for example, Japanese Patent Application Laid-Open No. 60-192333).

[Problem M to be Solved by the Invention] However, the above-described resist pattern forming method, glass 1 to removal method, and substrate cleaning method have the following problems.

That is, first, in the resist pattern forming method, the development process is performed at least three times as described above.
The disadvantages are that more steps are required, the number of steps is large, and the processing is complicated. In addition, in this case, a large amount of multiple types of expensive solvents must be used, which increases the processing cost.In addition, from the viewpoint of safety management such as preventing fires and eliminating adverse effects on workers, a clean room is required for developing equipment and work areas. requires special equipment for ventilation, and
Since the developing step is carried out by the spin code method, a large amount of waste liquid is generated, which has the disadvantage that it is difficult to dispose of this waste liquid.

Furthermore, the resist removal method described above has the following drawbacks.

In other words, among the resist removal methods described above, method (2) using a strong oxidizing solvent has a limited range of applicability because the solvent used may act on the substrate underlying the resist and damage it. , for example, if the substrate has I on the surface
In the case of a substrate for a liquid crystal panel on which a TO film (transparent electrode film made of indium oxide containing tin) is formed, the solvent is ITOII! This method could not be applied because it would damage the

In addition, in the method (2) above using an organic solvent, it is usually necessary to heat the organic solvent in order to enhance the elution effect, which requires great consideration for safety, and also depends on the type of resist, process conditions, etc. In some cases, the used resist could not be completely removed using an organic solvent.

Incidentally, both of the above-mentioned methods (1) and (2) also have the problem of waste liquid treatment.

Furthermore, although the method (2) using oxygen plasma has an excellent resist removal effect, it requires a large-scale apparatus, increases equipment costs, and has the disadvantage that the substrate may be contaminated with metal.

Furthermore, among the conventional cleaning methods described above, the ultrasonic cleaning method using DI water etc. described in (a) is actually
I water or IPA aqueous solution is prepared separately in multiple tanks, and ultrasonic cleaning is performed by immersing in these various baths one after another, which requires a large number of steps and is complicated, and the substrate is damaged by the ultrasonic waves. Particularly, for example, in the case of a multilayer substrate in which a plurality of thin films are laminated on the surface, weak internal films may be intensively damaged.

In addition, the method (b) of mechanically peeling off with a brush etc. is effective for strong glass substrates or unprocessed wafers, etc., but for multi-NWA substrates that have a soft thin film layer inside, Or thinned X
It could not be applied to substrates such as line masks due to their mechanical strength. Incidentally, both of these methods (a> and (b)) also have the problem of waste liquid treatment.

Furthermore, the method (C) using the expansion force of gas, etc. does not have the problems mentioned in (a) and (b) above, but it involves housing the substrate in a high-pressure container and rapidly changing the internal pressure. Therefore, there is a risk that the substrate may be damaged by the impact, and it cannot be applied particularly to thin-film X-ray masks with weak mechanical strength or multilayer film substrates having soft thin film layers inside.

An object of the present invention is to provide a method for forming a resist pattern, a method for removing a resist, and a method for cleaning a substrate, which eliminate the above-mentioned drawbacks.

[Means for Solving the Problems] The present invention is based on the discovery of a novel fact that a developing effect is obtained when a substrate after exposure processing is immersed in a high-pressure liquid below the critical pressure for a certain period of time, and the present invention The discovery of a new fact that this resist removal effect can be obtained by immersing a substrate with foreign matter in a high-pressure liquid below the critical pressure for a certain period of time, and immersing a substrate with foreign matter in a high-pressure liquid below the critical pressure. This was made based on the discovery of the novel fact that the foreign matter can be removed and a cleaning effect can be obtained by using the method, and the device has the following configurations. (1) In a resist pattern forming method in which a resist pattern is formed on the substrate surface by subjecting a resist coated on the substrate surface to exposure treatment and developing it, the development process is performed on the exposed substrate. 1. A resist pattern forming method, characterized in that the method is carried out by immersing at least a portion on which the resist is formed in a high-pressure liquid having a pressure lower than a critical pressure.

(2) In a resist removal method for removing resist applied to a substrate surface, at least a portion of the substrate to which the resist is attached is immersed in a high-pressure liquid with a pressure lower than the critical pressure. Featured resist removal method.

(3) A substrate cleaning method for removing foreign matter adhering to a substrate, characterized in that cleaning is performed by immersing the substrate in a high-pressure liquid below a critical pressure.

[Function] In the above configuration (1), the exposure treatment causes a main chain scission reaction in the resist, resulting in a lower molecular weight (in the case of a positive resist), or conversely, a crosslinking reaction occurs, resulting in a higher molecular weight. In the case of negative-tone resists, this may cause a significant difference in molecular weight between the areas exposed to radiation and those that are not, or in the case of novolac-based photoresists such as Hoechst's A21350 (trade name). As shown in the figure, a unique functional group is generated by a photochemical reaction in the area irradiated with radiation, resulting in a difference in the elution rate with respect to the solvent between the area irradiated with radiation and the area not irradiated with radiation.

Next, when at least the portion of the exposed substrate on which the resist is formed is immersed in a high-pressure liquid below the critical pressure for a certain period of time, the portion having a low molecular weight or the portion having a high elution rate is selectively removed. The resist is eluted into the high-pressure liquid and developed to form a resist pattern.

Further, in the configuration (2), by immersing at least a portion of the substrate to which the resist is attached in a high-pressure liquid below the critical pressure for a certain period of time, the resist is eluted into the high-pressure liquid. It has been confirmed that the resist can be removed by

Furthermore, according to the configuration (3), it has been confirmed that foreign matter adhering to the substrate is removed and the substrate is cleaned.

Here, critical pressure refers to the pressure at the boundary where a substance becomes a supercritical fluid in the narrow sense. Note that supercritical fluid, in a broad sense, refers to a state in which it does not liquefy even when compressed to a high density, that is,
A general term for gases that have been heated above the critical temperature unique to the substance, and also includes low-density states that exhibit properties close to ideal gases, but supercritical fluids in the narrow sense refer to gases that are heated to a temperature that is significantly higher than normal pressure. It means a fluid that is compressed to a high density under pressure (for example, several tens of atmospheres), for example, in extreme cases, compressed to a high density that is close to or higher than that of a liquid.

Further, the term "high-pressure liquid" refers to a liquid in which a substance in a gaseous or liquid phase at normal pressure is maintained at a temperature below its critical temperature, and its pressure is maintained significantly higher than normal pressure (for example, 10 atmospheres or more).

According to the inventors' considerations, it is assumed that in such a high-pressure liquid, the movement of individual molecules is extremely active, and for this reason, individual molecules can easily penetrate into substances that cannot be penetrated under normal pressure conditions. It is thought that it penetrates and elutes it.

[Example] Hereinafter, a resist pattern forming method, a resist removing method, and a substrate cleaning method according to an example of the present invention will be described in detail with reference to the drawings.

1. Patterning of resist First, PMMA, which is a positive type electron beam resist, is applied to a thickness of about 5000 angstroms on the surface of a disk-shaped silicon wafer having a diameter of 3 inches, and then exposed to light using an electron beam lithography system. In this case, the acceleration voltage is 20 KV, the dose is 50 μC/aJ, and the minimum line width of the exposure pattern is 0.5 μm in a repeating pattern of lines and spaces.

Next, this exposed silicon wafer is immersed in a high-pressure liquid for development. In this case, the high pressure liquid is trifluoromethane (CF3L critical temperature 25.9°C, critical pressure 4
A pressure of 8.1 atm and a critical density of 0.525 g/cm3) are used.

FIGS. 1 and 2 are diagrams showing the situation of this development process.

In the figure, reference numeral 1 denotes a high-pressure container, and a net-like holder 2 is provided approximately in the center of the high-pressure container 1. As shown in FIG.

When performing development, first, the exposed substrate 3 is placed on the net-like holder 2. At this time, the exposed resist 4 formed on the substrate 3 faces downward in the figure. In addition,
Depending on the case, it may also be placed facing upwards.

Next, high-pressure (several tens of atmospheres) trifluoromethane maintained at 20° C. is introduced into the high-pressure container 1, cooled with, for example, dry ice, through an inlet (not shown). After introduction,
Close the inlet and seal the high pressure container (2). Afterwards, the dry ice is removed and the high pressure container 1 is brought to room temperature (2
0°C).

As shown in Figure 1, the introduced trifluoromethane
The substrate 3 is immersed in the liquid layer portion 5, although the liquid layer portion 5 and the gas layer portion (steam portion) 6 exist separately. At this time, the internal pressure of the high-pressure vessel 1 was 40 atm.

This state is maintained for 4 hours. As a result, as shown in FIG. 2, the resist 4 on the substrate 3 was developed to form an uneven pattern along the exposure pattern.

The depth of the resist pattern thus formed was measured with a stylus-type step meter (Tally Step, manufactured by Rank Taylor) and found to be 3200 angstroms.

2; Resist pattern This example shows an example in which a thin film X-ray mask is used as the substrate and the X-ray mask is immersed in a supercritical fluid containing an organic solvent. It is.

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

A disk-shaped silicon wafer with a diameter of 3 inches (thickness: 4
00 Jlm> by reactive sputtering method.
A thin rgA (thickness: 2 μm) of A blank for an X-ray mask was prepared by forming a thin film of tantalum (thickness: 10.6 μm) as an X-ray absorber on the surface of the silicon wafer by sputtering. obtain.

Next, a photoresist A21350J-(
A film (thickness: 2.5μ111) of Hoechst Co., Ltd. (trade name) is formed, and a film of SiO□Jlllj (thickness: 100
0 angstrom), and finally, an electron beam resist PMMA was formed on the Si02'IN by a spin coating method.
A film (thickness, 3000 angstroms) is formed.

FIG. 3 is a cross-sectional view of the thus obtained X-ray mask blank, in which reference numeral 1 is the support frame, 12 is the thinned silicon wafer, 13 is the tantalum film, and 14 is the first film.・Resist film, 15 is SiO□ film, 16 is PM
M A WA.

Next, the electron beam resist PMIV[A of the X-ray mask blank is exposed by an electron beam drawing device. At this time, the acceleration voltage of the electron beam was 20KV, and the dose was 60KV.
Jie/cm2. The minimum dimension of a figure consisting of lines and spaces is 0.5 μm.

The substrate thus exposed is placed in a high-pressure container 1 shown in the above-mentioned drawing, and developed in substantially the same manner as in the first embodiment.

In this case, the difference from Example 1 is that high pressure liquid (CF
0.5% by weight of methyl isobutyl ketone (
MiBK) is added and the temperature of the high pressure vessel 1 is set to 1.
The point is to maintain at 6°C for 10 minutes.

As a result, uneven bumps are formed on the PMMA resist. In this case, the depth of the pattern was 3000 angstroms as measured by the stylus step meter. Moreover, the above-mentioned S! It was confirmed that the 02 film was completely exposed.

As mentioned above, in this example, the development time could be significantly shortened compared to the above example.

This embodiment is a method for removing and cleaning the used resist of the X-ray mask in which the resist pattern was formed in the second embodiment.

First, according to Example 2, PMMA electron beam resist 1
Active ion etching (RIE) was performed on the resist pattern formed in S.6 (FIG. 4), and the S! Transfer the resist pattern to the 02 film 1.5,
Next, RIE using oxygen gas was performed on the PMMA resist film 16 and SiO2 [15] on which these patterns were formed.
This pattern is applied to the photoresist AZ13.
50, TM 14. Thereafter, RIE using CL2 gas is performed on the film 14 of this photoresist 1-AZ1350J to etch the tantalum film 13 which is the X-ray absorber, thereby removing the tantalum formed on the silicon thin film 1-2. A desired pattern can be formed on the film 13. FIG. 4 is a sectional view showing the substrate thus obtained. By the way, on this tantalum film 13 there is a used glass I'' (A, Zi 350) with a thickness of about 1.5 μm.
J) 14a remains.

Therefore, next, the substrate on which the used resist i 4 a remains is placed on the high-pressure container 1 shown in FIG. In the step, the used resist L4a is sufficiently thoroughly mixed with By trifluoride methane and MiBK in an amount of 7% by weight, and the high-pressure container is maintained at 25° C. for 45 minutes. As a result, the used resist is removed and the substrate is cleaned. Note that at this time, the pressure inside the high-pressure container was 45 atmospheres.

After removing and cleaning the used resist in this way, the substrate was inspected with the naked eye by oblique light illumination using a condensing lamp, and
As a result of 50x magnification observation with an optical M microscope, no residual resist or other foreign matter was observed, and it was confirmed that the surface was extremely clean and that the 2 μm thick SiN film was not damaged at all. has been done.

(4; Method for removing resist) In this example, an electroluminescent (EL) panel with eight thin films laminated on its surface was used as the substrate, and photoresist A21350J was used for the top layer ALlli. This is an example in which a used resist remaining on a resist having a wiring pattern formed thereon is removed and cleaned.

The substrate on which the used resist remains is placed on the net-like holder 2 of the high-pressure container 1 shown in FIG. A submerging amount of methane trifluoride and an amount of 5% by weight of MiBK are introduced, and the high pressure vessel is maintained at 25° C. for 30 minutes. At this time, the pressure inside the high-pressure container was 45 atmospheres. As a result, the used resist was removed and cleaned.

After removing and cleaning the used resist in this way, the substrate was observed with the naked eye under oblique illumination using a condensing lamp, and
As a result of observation under 50x magnification using an optical microscope, no residual foreign matter was found in the resist, and the surface was extremely clean, and in the operation test of the EL panel, no damage to the internal layers occurred at all. It was confirmed that there was no such thing.

According to the above embodiments, a solvent with a strong oxidizing effect is used, or mechanical vibration (in the case of using the above-mentioned ultrasonic waves) or impact force (in the case of using the expansion force of the above-mentioned gas) is applied to the entire substrate. There is no need to apply supercritical fluid, and the molecules of the supercritical fluid exert the necessary action only on the resist that comes in direct contact with it to develop, remove, or clean it, so it can be developed, removed, or cleaned without damaging the underlying substrate or thin film. Can be washed.

Furthermore, the liquid used is a relatively inert gas, or a gas to which a very small amount of an organic solvent is added.
Since the method is simply immersed in these for a certain period of time, the process is extremely simple, and post-processing such as waste liquid treatment is also much easier than in the past, which is an excellent advantage.

In the above embodiments, trifluoromethane was used as the high-pressure liquid, but this is not necessarily limited to trifluoride methane. For example, Ar, Kr, etc.
, other inert substances such as Xe or CO2,
In addition, although they are somewhat inferior in safety against fire etc. compared to these inert substances, for example, lower hydrocarbons such as CH4, C
Fluorocarbons other than F and H can also be used.

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

[Effects of the Invention] As described in detail above, the present invention enables development, resist removal or This method is designed to clean the substrate, which simplifies the process, eliminates the risk of substrate damage, and has the excellent effect of significantly reducing waste liquid disposal.

[Brief explanation of drawings]

1 and 2 are diagrams showing the development process in the resist pattern forming method according to the embodiment of the present invention, FIG. 3 is a cross-sectional view showing an X-ray mask blank, and FIG. 4 is a diagram showing residual resist. FIG. 3 is a cross-sectional view showing the X-ray mask in an attached state. Process: High pressure container, 3: Exposed substrate, 4: Exposed resist, 7: High pressure liquid, 14a: Used resist.

Claims (3)

[Claims] (1) In a resist pattern forming method in which a resist pattern is formed on the substrate surface by subjecting a resist coated on the substrate surface to exposure treatment and developing it, the development process is performed on the exposed substrate. 1. A resist pattern forming method, characterized in that the method is carried out by immersing at least a portion on which the resist is formed in a high-pressure liquid having a pressure lower than a critical pressure. (2) In a resist removal method for removing resist applied to a substrate surface, at least a portion of the substrate to which the resist is attached is immersed in a high-pressure liquid with a pressure lower than the critical pressure. Featured resist removal method. (3) A substrate cleaning method for removing foreign matter adhering to a substrate, characterized in that cleaning is performed by immersing the substrate in a high-pressure liquid below a critical pressure.