JPS60192333A - Method for removal of organic coated and hardened film - Google Patents

Abstract

PURPOSE:To prevent the contamination of a protective film by impurities and the deterioration of element characteristics, to prevent the lowering of yield of production as well as to easily obtain a method in which a treatment solution will be reused by a method wherein, after a substrate and liquid gas or supercritical gas have been contacted with each other, the gas is expanded by changing its temperature and/or the condition of pressure. CONSTITUTION:After a substrate, whereon an organic coated and hardened film is joined together, and liquefied gas or supercritical gas have been contacted, the gas is expanded by changing its temperature and/or the condition of pressure. Non-oxidizing gas such as CO2, NH3, N2 and the like can be used as liquefied gas or supercritical gas, but CO2 is suitable taking into consideration of advantages in cost and operation. Also, a gaseous organic solvent can be used at the normal temperature, and propane, butane, methyl chloride and the like can be used as the organic solvent. When liquefied carbonic acid gas is used, as it is hardly infiltrated completely into the interior of the organic coated and hardened film and the like such as a photoresist coated film, or on the interface between said films and the substrate, it is desirable in this case that an organic solvent of high solubility is mixed into carbonic acid gas.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for removing an organic coating cured film from a substrate to which the organic coating cured film is bonded, and particularly to a method for removing a photoresist coating film from a semiconductor wafer. A method suitable for

[Background of the invention]

The semiconductor wafer is a Si single crystal plate with 5i02. After a pupil retaining film such as SiN or aluminum is formed, a photoresist material is applied to the surface of these protective films, polymerized into a predetermined pattern by exposure to light in a predetermined pattern, and then a photoresist coating film in a predetermined pattern is formed by pattern etching. A protective film is then formed, and then impurities are doped. It is necessary to remove the photoresist coating film from the semiconductor wafer after such pattern etching has been completed. Conventionally, a method for removing such a photoresist coating has been to dissolve the photoresist coating using a strong oxidizing agent such as hot sulfuric acid, sulfuric acid, or hydrogen peroxide. However, the method using such a strong oxidizing agent has the drawback that the photoresist film components are dissolved in the processing agent, making it difficult to reuse the processing solution and short-lived the processing solution. Furthermore, depending on the processing method, there is a possibility that the underlying material of the photoresist film may be attacked. On the other hand, in consideration of the chemical resistance of the underlying material of the photoresist film, a method of removing the photoresist coating film using a special removing agent such as a phenolic organic material or a halogenated organic solvent has also been used. However, in methods using these organic solvents, post-treatment of the solvent is necessary for environmental protection, and problems arise in handling since the solvent is a flammable chemical. Furthermore, an ashing method using low-temperature oxygen plasma has been used, but this method cannot remove the heavy metals contained in the photoresist film, and these heavy metals remain on the semiconductor wafer surface even after the photoresist film is removed. Treatment to remove heavy metals is required.

The problems that arise with conventional photoresist coating film removal methods are deterioration of device characteristics due to abnormal diffusion of the processing solution,
The current situation is that contamination of Sing by impurities, destabilization of device characteristics, deterioration of dielectric breakdown voltage, etc. are reducing the number of droplets in the device.

[Purpose of the invention]

The present invention provides a method for removing a cured organic coating film that prevents contamination of a protective film such as 5i02 due to impurities and deterioration of device characteristics, prevents deterioration of small droplets of the device, and allows easy reuse of the processing solution. Our goal is to provide the following.

[Summary of the invention]

The present invention provides a method for physically peeling off an organic coated cured film such as a photoresist coated film without using phenomena such as dissolution, chemical peeling, or oxidation, and in which the organic coated cured film is bonded. In a method for removing an organic coated cured film from a substrate, the substrate on which the organic coated cured film is bonded is brought into contact with a liquefied gas, which is a supercritical gas, and then the temperature and/or pressure conditions of the gas are changed. expanding the gas;
The organic coating cured film is removed from the substrate by this expansion force.

In the present invention, the substrate to which the cured organic film is bonded is brought into contact with supercritical gas under high pressure, and the liquefied gas or supercritical gas is applied to the cured organic film itself or to the interface between the cured organic film and the substrate. The pressure of the liquefied gas supercritical gas is reduced or the temperature of the liquefied gas or supercritical gas is increased.

As a result, the dissolved liquefied scum or dissolved supercritical gas existing within the cured organic film or at the interface between the cured organic film and the substrate expands, and the expansion force causes the cured organic film to be peeled off from the substrate. Various liquefied gas extraction methods and supercritical gas extraction methods have been proposed that utilize the properties of liquefied gas or supercritical gas as a solvent. These methods utilize the properties of solvents, such as (A) high dissolving power, (B) selectivity, and (C) ease of separating the extract from the solvent.

The present invention utilizes (A) the solubility of a solvent gas and (B) the expansion power of liquefied gas or supercritical gas by reducing pressure or increasing temperature, and is different from conventional extraction methods in principle and purpose.

Here, the supercritical gas refers to a gas that is in a state of not less than a critical temperature and not less than a critical pressure in a pressure-temperature phase diagram. In the pressure-temperature phase diagram, liquefied gas is
A substance that is in a gaseous state at normal temperatures under atmospheric pressure and at a pressure above the saturated vapor pressure line.

In the present invention, the organic solvent which is gaseous at normal temperature as a liquefied gas or a supercritical gas can be used alone.

Propane, butane, methyl chloride, etc. can be used as such an organic solvent. These gaseous organic solvents can be turned into liquefied gases or supercritical gases by subjecting them to high pressure and low temperature.

In the case of liquefied carbon dioxide gas, it is difficult to completely penetrate into the interior of organic coated cured films such as photoresist coatings or the interface between these films and the substrate, so in this case, an organic solvent with high solubility is mixed with carbon dioxide gas. Then, it is desirable. When a liquefied gas is rapidly depressurized by mixing an organic solvent, it serves to alleviate the shock caused by the rapid depressurization. Organic solvents with high mutual solubility with liquefied carbon dioxide include hydrocarbons,
Examples include organic solvents such as logenated hydrocarbons, alcohols, and ketones. Hydrocarbon organic solvents, such as hexane petroleum ether, benzene, toluene, etc.
The medium completely dissolves in liquefied carbon dioxide. Furthermore, organic solvents such as dichloromethane and fluorocarbons are insoluble in a static state, but dissolve when stirred. Alcohol-based organic solvents, such as ethanol (anhydrous), completely dissolve in liquefied carbon dioxide gas, while ethanol (hydrated) partially dissolves in liquefied carbon dioxide gas. Further, a ketone organic solvent such as acetone completely dissolves in liquefied carbon dioxide. Therefore, the organic solvent to be mixed with the liquefied carbon dioxide gas should be selected by comprehensively considering the solubility of the organic coating cured film and the property of not damaging the substrate. Even in the case of supercritical gas, it is desirable to mix an organic solvent with the supercritical gas in order to completely dissolve the cured coating film and penetrate the interface between the cured organic coating film and the substrate. .

When an organic solvent is used, the amount of organic solvent used can be small because a large amount of solvent gas is dissolved in a small amount of organic solvent. FIG. 1 shows experimental data showing the overall solubility of liquefied carbon dioxide gas (hereinafter abbreviated as -CO2) and an aqueous ethyl alcohol solution. The horizontal axis is the temperature, the vertical axis is the amount of L-CO2 dissolved in the aqueous ethyl alcohol solution, and the amount of the aqueous ethyl alcohol solution dissolved in the L CCh, and the alcohol concentration of the aqueous ethyl alcohol solution is the parameter. From Figure 1, if the temperature is constant at 16C and the alcohol concentration of ethyl alcohol is plotted on the horizontal axis, it is shown as in Figure 2, and the concentration is 90C.
It can be seen that a considerable amount of L CO2 is dissolved in the ethyl alcohol aqueous solution at vol 1% or more.

[Embodiments of the invention]

The present invention will be explained in detail by way of examples.

Example 1 After pattern-etched photoresist coated film of approximately 10 μm was brought into contact with L-COx in a vessel at room temperature for a predetermined period of time, the pressure inside the vessel was rapidly increased to atmospheric pressure. The pressure was reduced.

The photoresist coating was cleanly peeled off from the substrate.

Example 2 A power unit with a photoresist coating film thickness of about 10 μm after pattern etching is brought into contact with supercritical carbon dioxide gas at a temperature of 351 r in a vessel, and the pressure inside the vessel is rapidly raised to atmospheric pressure. The pressure was reduced to At this time, the direction of gas suction was parallel to the flat surface of the semiconductor wafer. As a result, the photoresist coating film was neatly separated from the substrate in small pieces, and the wafer was not damaged.

Example 3 A photoresist coated film with a thickness of approximately 10μ and a photoresist coated film that has been subjected to no-turn etching is brought into contact with a mixed solvent of L Co2 and ethyl alcohol in a vessel at room temperature, and the pressure inside the vessel is set to atmospheric pressure. The pressure was rapidly reduced to . As a result, the photoresist coating was clearly peeled off from the substrate. Note that the direction of gas suction was the same as in Example 1, and there was no damage to the unit. In this implementation U, L
It is thought that the presence of ethyl alcohol in COa eased the impact during depressurization, so no damage to the wafer occurred.

〔Effect of the invention〕

As described above, according to the present invention, since the organic coating cured film bonded to the substrate is physically peeled off and removed, there is no deterioration of device characteristics caused by oxidative decomposition or dissolution caused by chemicals. Leads to improvement. In addition, when a protective film made of a thin oxide film is provided like a photoresist coating film, there is no contamination of Sing by impurities, destabilization of device characteristics, and deterioration of dielectric strength, and there is no need for cleaning to remove the oxide film in the next process. . Furthermore, since the organic coated cured film such as the photoresist coated film that has been peeled off and removed exists as a solid substance in the processing solution, it is easy to recover, and therefore, the drainage treatment is greatly simplified.

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing the overall solubility of liquefied carbon dioxide and an aqueous ethyl alcohol solution. (-)4rjlpl'm'IO94I-C41J-1st
Continued page ■ Inventor Yoshinori Sahara 3] Saiwai-cho, Hitachi City 0 Inventor Hide Yagi 3] Saiwai-cho, Hitachi City 1 LQ-

Claims (1)

[Claims] 1. A method for removing an organic coated cured film from a substrate to which the organic coated cured film is bonded, the method comprising: bringing the substrate to which the organic coated cured film is bonded into contact with liquefied gas or supercritical gas; A method for removing an organic coated cured film, characterized in that the temperature and/or pressure conditions of the gas are then changed to expand the gas. 2. The method for removing an organic coated cured film according to claim 1, wherein the gas contains an organic solvent. 3. The method for removing an organic coating cured film according to claim 1, wherein the substrate is a semiconductor wafer and the organic coating cured film is made of a photoresist material. 4. The semiconductor wafer is a Si single crystal plate with a thickness of 5 iOa. 4. The method of removing a cured organic coating film according to claim 3, wherein a protective film such as SiN or At is formed, and the photoresist material and the protective film are pattern-etched for 14 days. 5. The method for removing an organic coating cured film according to claim 3 or 4, wherein the photoresist material is of a negative or positive type.