JP2002192089A - Cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning a substrate by satisfactory cleaning action at a low cost without destructing the environment. SOLUTION: This cleaning method comprises immersing the substrate as the subject to be cleaned in a cleaning bath 10 filled with a cleaning liquid 21 containing H2O2(hydrogen peroxide) and O3(ozone), heating the liquid 21 or supplying a high-energy ray such as an ultraviolet ray and an ultrasonic wave to the liquid 21 to generate active oxygen radicals consisting mainly of OH(hydroxyl radical) from H2O2(hydrogen peroxide) and O3(ozone) and decomposing contaminants on the surface of the substrate with the generated radicals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method, and more particularly, to a wide range of fine particles, metals, molecular organic substances and photoresists adhered to a substrate to be processed such as a semiconductor silicon wafer or a liquid crystal display glass substrate. The present invention relates to a cleaning method for oxidatively decomposing and removing photoresist residues.

[0002]

2. Description of the Related Art Conventionally, in a wet process for manufacturing a semiconductor or a liquid crystal display, a cleaning method of cleaning using a mixture of hydrogen peroxide and a chemical such as sulfuric acid, hydrochloric acid, and ammonia has been used.

[0003]

However, since the acid and the alkali are expensive chemicals, there is a problem that the material cost of the cleaning agent itself is considerably high.

[0004] Further, when chemicals such as acids and alkalis having long-lasting reactivity are used, the reactivity remains in the waste liquid remaining as a result of the cleaning method using these chemicals. Therefore, if these waste liquids are disposed of as they are, they will cause environmental destruction and environmental pollution. Need to be reused. Therefore, such waste liquid treatment and purification of waste liquid containing acids and alkalis is troublesome and costly, and has a problem of increasing the production cost of the product.

On the other hand, a method of washing with ozone or hydrogen peroxide is also known, but only organic substances having a carbon-carbon double bond can be decomposed using ozone, and inorganic substances and organic substances can be decomposed. Substances having no carbon-carbon double bond, such as metals, cannot be decomposed and have a problem that a sufficient cleaning effect cannot be obtained.

The present invention has been made to solve the above-mentioned problems of the conventional cleaning method. That is, an object of the present invention is to provide a cleaning method which has a sufficient cleaning power, is low in cost, and has no fear of environmental destruction.

[0007]

SUMMARY OF THE INVENTION The cleaning method of the present invention comprises cleaning a substrate surface in the presence of active oxygen species generated by supplying O ₃ (ozone) to ultrapure water containing an active oxygen source. Features.

In the above-mentioned cleaning method, “active oxygen source” includes, for example, H ₂ O ₂ (hydrogen peroxide), O ₃ (ozone),
Alternatively, it refers to a mixture of H ₂ O ₂ (hydrogen peroxide) and O ₃ (ozone).

In the above-mentioned cleaning method, the above-mentioned "active oxygen species" refers to peroxide and its decomposition intermediate product, and ozone is not included in the active oxygen species.

More specifically, examples of reactive oxygen species used in the present invention include O ₂ ⁻ (superoxide), HO ₂ (hydroperoxide), OH • (hydroxy radical), and O ₂ ^* (excitation). One or more substances or mixtures selected from the group consisting of oxygen).

In the above cleaning method, the active oxygen species is obtained by mixing O ₃ (ozone) and H ₂ O ₂ (hydrogen peroxide), or by mixing O ₃ (ozone) and H ₂ O.
₂ (hydrogen peroxide) is generated by irradiating 1 or 2 of the group consisting of hydrogen peroxide with high energy rays such as ultraviolet rays or ultrasonic waves, or by heating.

Specifically, O₃(Ozone) and H₂O
₂(Hydrogen peroxide), O ₃(Ozone)
Irradiate with ultraviolet light or ultrasonic waves in the presence or warm
Method, H₂O₂UV or in the presence of (hydrogen peroxide)
Method of irradiating or heating ultrasonic waves, O₃(Ozo
N) and H₂O₂UV or in the presence of (hydrogen peroxide)
There is a possibility of irradiating ultrasonic waves or heating.
You.

However, in the method of supplying ultrasonic waves in the presence of O ₃ (ozone), a chemical such as a pH adjuster is not used.

Further, H ₂ O ₂ (hydrogen peroxide) and O ₃ (ozone) used in the above-mentioned cleaning method are H ₂ O ₂ (hydrogen peroxide).
Is preferably 30% or less, and ozone gas is preferably used in a range of 200 g / Nm ³ or less.

The upper limit of the preferable range of H ₂ O ₂ (hydrogen peroxide) and O ₃ (ozone) used in the above-mentioned cleaning method is set to the above value in order to operate the apparatus in a safe state.

Another cleaning method of the present invention is characterized in that the surface of a substrate is cleaned in the presence of active oxygen species generated by supplying a high energy beam to H ₂ O ₂ (hydrogen peroxide).

In the above method, the "high energy ray" includes, for example, ultraviolet rays and ultrasonic waves.

The ultraviolet light used has an absorption band wavelength range of 100.
Ultraviolet light of -400 nm is preferred.

The ultrasonic wave used has a frequency of 10 KH.
Ultrasound of z-5 MHz is preferred.

The preferable range of the ultraviolet absorption band and the preferable range of the frequency of the ultrasonic wave are set to the above ranges, respectively, because a sufficient amount of the active oxygen species can be obtained when the ultraviolet and the ultrasonic waves outside the above ranges are used. It is not generated.

Further, in the above-described cleaning method, cleaning may be performed while heating the cleaning liquid. In that case, the temperature of the cleaning liquid is 8
It is preferable to maintain the temperature at 0 to 150 ° C. The reason why the preferable range of the heating temperature of the cleaning liquid is set to the above range is that if the temperature is below the above range, the effect of the heating cannot be sufficiently expected,
Conversely, if the ratio exceeds the above range, the decomposition rate of hydrogen peroxide and ozone becomes too high, and the existence time of active oxygen species becomes short.

Further, another cleaning method of the present invention includes a step of cleaning the surface of a substrate in the presence of an active oxygen species, and a step of cleaning the surface of the substrate with a water-soluble fluoride. . Examples of the water-soluble fluoride used in this cleaning method include HF and NH ₄ F.

According to the cleaning method of the present invention, since the substrate is cleaned using an active oxygen species without using an acid, the substrate can be cleaned at low cost without generating a waste liquid requiring waste liquid treatment. I can do it.

The active oxygen species used in the present invention is easily consumed by activated carbon and reduced to H ₂ O or O ₂ ,
It can be discharged as it is after the activated carbon treatment.

Therefore, it is possible to provide an environmentally friendly cleaning method in which waste liquid treatment after use is easy.

[0026]

Embodiments of the present invention will be described below. FIG. 1 is a diagram schematically illustrating a schematic configuration of a cleaning apparatus for performing a cleaning method according to the present embodiment.

FIG. 1A shows a schematic configuration of a cleaning apparatus used in a batch type cleaning system. As shown in FIG. 1A, the cleaning apparatus according to the present embodiment includes a cleaning bath 10, a cleaning liquid supply system (not shown) for supplying a cleaning liquid to the cleaning bath, and ozone water in the cleaning bath 10. The apparatus includes an ozone water producing apparatus 30 to be supplied, and an ultrasonic oscillator (MS) 40 that oscillates ultrasonic waves (megasonic) into the cleaning liquid in the cleaning bath 10. As shown in FIG. 1 _{(a), H} 2 O
_{The 2} adding device 60 may directly add H ₂ O ₂ into the cleaning bath 10, or in the middle of a pipe for supplying O ₃ (ozone) water from the O ₃ (ozone) water producing device into the cleaning bath 10. May be added.

Further, the cleaning bath 10 may further include a heater for heating the cleaning liquid, and an ultraviolet irradiation lamp (UV) as a high energy beam irradiation device.

In order to carry out the cleaning method of the present embodiment, first, the cleaning bath 10 is filled with the cleaning liquid 21, and the object to be cleaned, for example, a substrate 50 such as a silicon wafer is immersed in the cleaning liquid 21. In this state, the ultrasonic oscillation device (M
S) Activate 40. Then, H ₂ O in the cleaning solution
₂ (hydrogen peroxide) and O ₃ (ozone) are irradiated with high energy rays to activate oxygen atoms, and as shown in FIG. 2A, O ₂ ⁻ (superoxide) and HO ₂ (hydro Peroxide), OH • (hydroxy radical), O
Highly reactive active oxygen species such as ₂ ^* (excited oxygen) are generated.

Since these active oxygen species exist for a relatively long time under the conditions as in the present embodiment, that is, under the condition where no acid or alkali is used, by maintaining this state, the above-mentioned active oxygen species can be obtained. Attack the resist layer on the silicon wafer. As shown in FIG. 2B, the active oxygen species decomposes the resist layer at the surface on the resist or at the interface between the resist and the silicon wafer.

In particular, OH (hydroxy radical) has a high decomposing power, and as shown in FIG. 2B, decomposes the resist layer to make the layer thinner and separates the resist layer from the interface with the silicon wafer.

As the decomposition proceeds further, the resist layer is separated from the surface of the silicon wafer and completely separated as shown in FIG. 2 (c), and the surface of the silicon wafer becomes clean.

The cleaning liquid 21 used in this embodiment is a hydrogen peroxide solution. In the cleaning method of the present embodiment, cleaning is performed using active oxygen species formed when energy such as ultraviolet light, ultrasonic waves, or heat is applied to hydrogen peroxide or ozone.

The mechanism will be described below.

When energy such as ultraviolet rays, ultrasonic waves, or heat is supplied to a substance which easily forms active oxygen, such as hydrogen peroxide or ozone, a substance having high reactivity is formed.

These are peroxides and their decomposition intermediate products. Specifically, O ₂ ⁻ (superoxide), HO ₂ (hydroperoxide), OH • (hydroxy radical), O ₂ ^* (excitation Oxygen) is considered to be one or more selected from the group consisting of:

If the above-mentioned highly reactive substances are now called "active oxygen species", it has been known that these reactive oxygen species have high reactivity in themselves, but when they are used together with acids and alkalis, However, since it is decomposed in an extremely short time, it has been difficult to apply the method to cleaning of a substrate or the like.

It is considered that these active oxygen species are generated as a mixture of the above-mentioned substances. Among them, the reactivity of OH. (Hydroxyl radical) is extremely high.
It is considered that the mixture of the above-mentioned active oxygen species mainly having (hydroxyl radical) exhibits a cleaning action.

The oxidation-reduction potential of the active oxygen species (25 ° C.)
Is shown.

[0040]

[Table 1] As shown in Table 1 above, OH • (hydroxy radical) has the highest redox potential of 2.81 V among the redox potentials of the main active oxygen species, and has a high ability to easily oxidatively decompose impurities. it is conceivable that.

The value of the oxidation-reduction potential is an index of the ability to oxidize the partner, and the higher the potential, the higher the cleaning ability tends to be.

As described above, in the cleaning method of this embodiment,
By applying energy such as ultraviolet rays, ultrasonic waves, and heat to hydrogen peroxide and ozone, the life of the active oxygen species is extended by activating under relatively mild conditions. This is a method of performing washing.

In particular, the reactivity of OH. (Hydroxyl radical) among the active oxygen species is extremely high, and OH. (Hydroxyl radical) in the cleaning solution is important.

In the cleaning method according to the present embodiment, it is preferable to perform cleaning with a water-soluble fluoride as a step after cleaning in the cleaning liquid. This is because, when various contaminants such as metals, organic substances, and particles are attached to the surface of the object to be cleaned having reactivity with the active oxygen species such as a silicon wafer, all the contaminants are removed from the surface of the object to be cleaned. This is because the entire surface may be oxidized before the removal, and contaminants remaining on the surface without being removed may be taken in under the oxide film.

In such a case, after cleaning in the presence of the above-mentioned active oxygen species, the oxide film formed on the object to be processed is subjected to HF.
And water-soluble fluoride such as NH ₄ F,
This is because the surface of the object to be processed can be slightly scraped to remove the contaminants together with the oxide film.

According to the cleaning method of the present invention, since the substrate is cleaned using an active oxygen species without using an acid, the substrate can be cleaned at low cost without generating a waste liquid which requires waste liquid treatment. I can do it.

The active oxygen species used in the present invention is easily consumed by activated carbon and reduced to H ₂ O or O ₂ ,
It can be discharged as it is after the activated carbon treatment.

Accordingly, it is possible to provide a cleaning method in which waste liquid treatment after use is easy and there is no fear of environmental destruction.

Example An example of the present invention will be described below.

Photoresist stripping Using 30% H ₂ O ₂ , the temperature of the cleaning solution was about 80 ° C.
To wash it. As the photoresist, a chemically amplified resist was used, and a photoresist was applied to the surface of a silicon wafer to a thickness of 1 μm and cured to prepare a test piece. The test piece was immersed in 30% H ₂ O ₂ and heated to 80 ° C. for cleaning, and the photoresist was peeled off in one minute from the start of cleaning. At this time, the waste liquid could be easily decomposed with activated carbon, H ₂ O ₂ decomposing enzyme or the like.

(Comparative Example) An acid or alkali was added to the above-mentioned cleaning solution, and the same cleaning as above was performed. Although the cleaning action was almost the same as in the above example, a step of removing H ₂ O ₂ by performing a neutralization operation in the waste liquid treatment was required. Therefore, the total processing time including the waste liquid was more than twice as long as the present invention.

The present invention is not limited to the scope described in the above embodiment. For example, in the above embodiment, FIG.
The batch type washing method shown in FIG.
A cleaning apparatus for a spin cleaning method as shown in FIG. 1B may be used. In the cleaning device for the spin cleaning method, the ozone water is directly discharged from the O ₃ (ozone) water producing device directly to the sample substrate fixed on the stage without having a cleaning bath, An H ₂ O ₂ addition device, an ultraviolet irradiation device (UV), a heater, an ultrasonic oscillator (MS), and the like are provided in the middle of the pipe for carrying ozone water.
O 3 _(ozone) while being transported between the water system to be discharged to the sample substrate, hydrogen peroxide H _{2 O} 2 relative to O 3 _{(ozone) water,} UV, heat, ultrasound (mega Sonic) is being supplied.

[0053]

According to the cleaning method of the present invention, since the substrate is cleaned using an active oxygen species without using an acid, the substrate can be cleaned at low cost without generating a waste liquid requiring waste liquid treatment. Can be performed.

The active oxygen species used in the present invention is easily consumed by activated carbon and reduced to H ₂ O and O ₂ ,
It can be discharged as it is after the activated carbon treatment.

Therefore, it is possible to provide a cleaning method in which waste liquid treatment after use is easy and there is no fear of environmental destruction.

[Brief description of the drawings]

FIG. 1 is a view showing a cleaning apparatus according to the present invention.

FIG. 2 is a diagram showing a state when a cleaning method according to the present invention is performed.

[Explanation of symbols]

Reference numeral 10 denotes a cleaning bath, 20 denotes a cleaning liquid supply system, 30 denotes an ozone water producing apparatus, and 40 denotes an ultrasonic oscillator (high energy ray irradiation apparatus).

Claims (7)

[Claims] 1. A method for cleaning a substrate, comprising cleaning the substrate surface in the presence of active oxygen species generated by supplying O ₃ (ozone) to ultrapure water containing an active oxygen source. 2. A method for cleaning a substrate, comprising cleaning a substrate surface in the presence of active oxygen species generated by supplying a high energy ray to an active oxygen source. 3. The cleaning method according to claim 1, wherein the active oxygen source is H ₂ O ₂ (hydrogen peroxide), O _3.
(Ozone) or a mixture of H ₂ O ₂ (hydrogen peroxide) and O ₃ (ozone). 4. The cleaning method according to claim 1, wherein the cleaning is performed while heating. 5. The cleaning method according to claim 1, wherein the active oxygen species is a peroxide and a decomposition intermediate product thereof. 6. The cleaning method according to claim 4, wherein
The reactive oxygen species is O ₂ ⁻(Superoxide), HO
₂(Hydroperoxide), OH
Le), O₂ ^*1 selected from the group consisting of (excited oxygen)
Or a cleaning method comprising at least two. 7. A method for cleaning a substrate, comprising: a step of cleaning the surface of the substrate with ultrapure water containing active oxygen species; and a step of cleaning the surface of the substrate with a water-soluble fluoride.