JPH03261128A - Method of removing organic hardening film - Google Patents

Abstract

PURPOSE:To remove the organic hardening film on a substrate completely in a short time by soaking the substrate in an organic separating agent so as to separate the organic hardening film, and then bringing it into contact with liquefied gas or supercritical gas including the subcritical condition so as to remove the separated remnants and other pollutant. CONSTITUTION:A substrate, where an organic hardening film is made, is soaked in an organic separating agent so as to separate the hardening film from the substrate, and next the substrate is brought into contact with liquefied gas or supercritical gas including critical condition. That is, the carbon dioxide gas supplied from a carbon dioxide gas cylinder 1 is put into supercritical condition through a heater 2 and a pressurizer 3, and is supplied continuously to the pressure-resistant container 4 as a cleaning vessel, wherein semiconductor wafers from which organic hardening films are removed by treating them with, for example, organic separating agents are stocked, and the semiconductor wafers are brought into contact with supercritical carbon dioxide gas here and cleaned by it. Hereby, the organic hardening film can be removed from the substrate completely in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing an organic cured film from a substrate on which the organic cured film is formed, and in particular to a method for removing an organic cured film from a semiconductor wafer on which a photoresist film is formed. The present invention relates to a method for removing the above-mentioned peeling agent, peeling residue of the organic cured film, and other contaminants remaining on the semiconductor wafer after peeling off the organic cured film using a method.

In the production of standard LSIs, a thin film of SiO□, SiJ, aluminum, etc. is formed on a silicon single crystal plate, and then a photoresist is applied to the surface and subjected to lithography, etching, etc. Through the process, a predetermined pattern is formed on the thin film, and then the photoresist film is peeled off and cleaned, and then impurities are introduced.

In order to remove the photoresist film, a method is conventionally known in which the photoresist film is dissolved using a strong oxidizing agent such as hot sulfuric acid, sulfuric acid, or hydrogen peroxide. However, this method causes damage or breakage to the wafer surface, or dissolves photoresist film components in the oxidizing agent, which is the stripping agent, reducing its effectiveness as a stripping agent and shortening the life of the stripping agent. In addition, it has problems such as difficulty in reusing it. Furthermore, there is a possibility that the underlying material of the photoresist film may be attacked.

Therefore, in consideration of the chemical resistance of the underlying material of the photoresist film, a method is known in which a phenolic organic solvent or a halogenated organic solvent is used as a stripper to remove the photoresist film without damaging the underlying material. There is. However, this method of using an organic stripper is unfavorable from a safety and health standpoint because some organic solvents are toxic.
Furthermore, a large amount of cost is required for environmental protection measures.

On the other hand, in recent years, as a method for cleaning the surfaces of solid articles containing solid polymers such as quartz crystals and polyimide, Patent Application Publication No. 502137 of 1981 describes a method of cleaning the surfaces of solid articles such as carbon dioxide gas on the surfaces of such solid articles. By contacting supercritical gas,
A method of cleaning the surface has been proposed, and furthermore,
0-192333 discloses that after a semiconductor wafer on which a photoresist film is formed is brought into contact with a liquefied gas or a supercritical gas, the temperature and pressure conditions of the gas are varied to expand the gas and reduce its expansion force. A method has also been proposed in which a photoresist film is peeled off and removed from a semiconductor wafer. However, with this method, not only does it take a long time to remove the photoresist film, but the photoresist film is not completely removed, which has a detrimental effect on the characteristics of the resulting device, and also reduces its yield. .

The present invention has been made to solve the above-mentioned problems in the conventional peeling and removal method of organic cured films formed on substrates, especially photoresist films formed on semiconductor wafers. The object of the present invention is to provide a method for easily and completely removing an organic cured film from a substrate in a short time.

9, the method for removing an organic cured film according to the present invention is to immerse the substrate on which the organic cured film is formed in an organic @exfoliation solution to peel off the organic cured film from the substrate, and then to remove the organic cured film from the substrate using liquefied gas. Alternatively, the substrate is brought into contact with a supercritical gas containing a subcritical state to remove the stripping agent, peeling residue of the organic cured film, and other contaminants adhering to the substrate.

In the present invention, a subcritical gas refers to a gas in a state near the critical point in a pressure-temperature phase diagram, and since the gas is physically unstable in this region, it is not a supercritical gas. distinguished.

A supercritical gas is a gas in a state where the temperature is above the critical temperature and the pressure is above the critical pressure in the pressure-temperature phase diagram. In this state, the density increases due to a slight change in pressure or temperature. In the present invention, in particular, since it greatly affects the dissolution ability of substances,
Supercritical gas is preferably used.

Liquefied gas refers to gas that is in a pressure state equal to or higher than the saturated vapor pressure line in a pressure-temperature phase diagram and is gaseous under normal temperature conditions under atmospheric pressure.

In the present invention, carbon dioxide gas, nitrogen oxide, ethane, propane, etc. are used as the liquefied gas or the supercritical gas containing a subcritical state. In particular, carbon dioxide gas is nonflammable, harmless,
It is inexpensive, and has a critical temperature of 31℃ and a critical pressure of 7.
At 9.2 atmospheres, it is easy to handle, and supercritical carbon dioxide gas has low viscosity and can penetrate into the fine details of the substrate, eliminating the aforementioned contaminants that remain attached to the substrate. It is preferably used in the present invention because it can be rapidly dissolved and removed.

In the present invention, the organic stripping agent used to remove the organic cured film from the substrate on which the organic cured film is formed, or the aromatic organic compound used as the ashes of the organic stripping agent, is heated in a liquefied gas or subcritical state. It can be blended with supercritical gas containing.

In particular, it has a relatively high dissolving power for organic stripping agents that remain attached to the substrate, but has a relatively low dissolving power for organic cured films such as photoresist films.
Thus, it is useful to blend an organic stripping agent or an aromatic organic compound used as a component thereof into a liquefied gas or a supercritical gas containing a subcritical state as a cleaning aid (entrainer).

Such aromatic organic compounds are not particularly limited, but preferably benzene, toluene,
In addition to aromatic hydrocarbons such as xylene, 0-dichlorobenzene, phenol, alkylbenzenesulfonic acid,
Examples include alkylhydroxybenzene.

According to an embodiment of the present invention, after the substrate having the organic cured film is immersed in an organic stripping agent to remove the organic cured film,
The substrate to which the organic stripping agent, cured film residue, and other contaminants such as oils and fats have adhered is placed in a pressure-resistant container, and liquefied gas or supercritical gas containing a subcritical state is passed through the container and brought into contact with the substrate. By causing the above pollutants to
Dissolved in the gas, the substrate is thus cleaned and cleaned.

As mentioned above, when an organic stripping agent or an aromatic compound as a component thereof is blended with a liquefied gas or a supercritical gas containing a subcritical state, after the gas is brought into contact with the substrate, such organic stripping agent is Only gas that does not contain stripping agents or aromatic compounds is brought into contact with the substrate.

Thus, after the gas is brought into contact with the substrate, the pressure of the gas containing contaminants is reduced or the temperature is increased, which significantly reduces the ability of the gas to dissolve those contaminants and organic stripping agents. Therefore, contaminants can be easily separated from the gas, and the gas can also be cooled, liquefied, and recycled for reuse. If a stripping agent is added to the gas, by appropriately selecting the pressure and temperature conditions mentioned above when separating contaminants and organic stripping agents, the gas can be released while retaining a certain proportion of the organic stripping agent. It can also be collected.

In the present invention, when the substrate is brought into contact with liquefied gas or supercritical gas containing a subcritical state, the temperature is -20 to 1
50°C, preferably in the range of o-100°C, and the pressure is 10 to 500 kg/cd, preferably 40 to 300 kg/cd.
kg/cd. Also, the contact time is usually
2 to 15 minutes is appropriate.

The present invention will be described below based on the drawings, taking as an example a case where supercritical carbon dioxide gas is used.

FIG. 1 shows an example of an apparatus configuration for carrying out the method of the present invention, in which carbon dioxide gas supplied from a carbon dioxide gas cylinder 1 is brought into a supercritical state through a heater 2 and a pressurizer 3.
For example, semiconductor wafers whose organic cured films have been removed by treatment with an organic stripping agent are continuously supplied to a pressure vessel 4 serving as a cleaning tank, where semiconductor wafers are exposed to supercritical carbon dioxide gas. touched and cleaned.

The supercritical carbon dioxide gas passes through a pressure-resistant container, is depressurized by a pressure reducing valve 5, and is then led to a separation tank 6 where it contains a stripping agent,
Photoresist film residue and other contaminants are separated from the bottom of the tank and discharged outside the system.

In addition, in order to combine organic stripping agent with supercritical carbon dioxide gas,
A stripping agent tank 10 may be connected to a supercritical carbon dioxide gas pipe 11 through a pipe system 9 equipped with a pump 7 and a valve 8 . The stripping agent is mixed with the supercritical carbon dioxide through this tubing so that it has a predetermined concentration in the supercritical carbon dioxide.

FIG. 2 shows another example of an apparatus configuration for carrying out the method of the present invention, in which carbon dioxide gas is recycled and reused. That is, the carbon dioxide gas supplied from the carbon dioxide gas cylinder 21 is
As in the case shown in the figure, it is made into a supercritical state through a pressurizer 22 and a heater 23, and is supplied to a pressure-resistant container 24, where it comes into contact with a semiconductor wafer and is cleaned. After that, a pressure reducing valve 25 and a separation tank 26 are removed. After being cooled and liquefied in a condenser 27, it is returned to the carbon dioxide cylinder 21.

According to the method of the present invention, the substrate on which the organic cured film is formed is immersed in an organic stripping agent to peel off the organic cured film, and then the substrate containing liquefied gas or a subcritical state is immersed. the stripping agent attached to the substrate by contacting the substrate with supercritical gas;
Since peeling residue and other contaminants from the organic cured film are removed, the organic cured film can be removed from the substrate in an extremely short time compared to the method of directly removing the organic cured film using liquefied gas or supercritical gas containing a subcritical state. In addition to being able to remove the organic cured film, it is also possible to completely remove the above-mentioned release agent, peeling residue of the organic cured film, and other contaminants such as oils and fats adhering to the substrate.

Furthermore, according to the method of the present invention, the liquefied gas containing various pollutants or the supercritical gas containing subcritical states can be purified from the gas by reducing the pressure or increasing the temperature. can be easily separated and the gas regenerated, so it can be reused without sacrificing its cleaning effectiveness.

Further, according to the present invention, there is no need for cleaning with a chlorinated organic solvent such as trichloride, perchlorene, or ethylene dichloride, or with chlorofluorocarbons, and there is no risk of causing environmental pollution.

The method of the present invention can also be suitably applied to cleaning wafers of compound semiconductors such as gallium and arsenic.

Although the present invention will be described below with reference to examples, the present invention is not limited to these examples in any way.

Example 1 A pattern-etched silicon wafer having a photoresist film with a thickness of 1 μm was coated with an organic stripping agent (Tokyo Ohka Kogyo Special Stripping Solution 71O) containing dichlorobenzene, phenol, and alkylbenzene sulfonic acid for 10 minutes.
After being immersed for 3 minutes at 0°C, it was placed in a pressure-resistant container 4 as shown in Fig. 1, and 100 kg/- of supercritical carbon dioxide gas was passed through it at 40°C for 10 minutes.

The supercritical carbon dioxide gas flowing out from the pressure container was depressurized by a pressure reducing valve 5, and after separating contaminants such as stripping agent and photoresist film residue in a separation tank 6, it was discharged to the outside of the system.

When the flow of supercritical carbon dioxide gas was stopped and the wafers removed from the pressure container were inspected, it was confirmed that no stripping agent remained on the wafers.

Example 2 500 pattern-etched silicon wafers having a 1 μm thick photoresist film were treated with the same organic stripping agent (Tokyo Ohka Kogyo Type Separation Liquid 710) as in Example 1 for 10 minutes.
After being immersed for 2 minutes at 0°C, the silicon wafer, with the release agent and part of the photoresist film still attached, has an internal volume of 50 I! as shown in FIG. The mixture was charged into a pressure-resistant container 24, and supercritical carbon dioxide gas at 40° C. and 120 kg/a+I was passed therethrough.

The pressure of the supercritical carbon dioxide flowing out from the pressure container was reduced to 50 kg/- by a pressure reducing valve 25, and contaminants such as stripping agent and photoresist film residue were separated in a separation tank 26. After the carbon dioxide gas was liquefied again in the condenser 25, it was returned to the carbon dioxide tank 21, and then sent into the pressure vessel 24 again by the pump 22.

The above operation was repeated to circulate supercritical carbon dioxide gas for 10 minutes. Thereafter, 500 silicon wafers were removed from the pressure container and inspected for quality, and it was confirmed that the cleaning effect was similar to that of conventional Freon cleaning.

Example 3 Ten silicon wafers that had undergone the same pattern etching as in Example 1 were treated with the same organic release agent as in Example 1 at 100°C.
After being immersed in water for 1 minute, the silicon wafer was placed in a pressure container 4 as shown in FIG. 1, with the release agent and a portion of the photoresist film still attached.

1200 kg of 40'C mixed with the above stripping agent via the pipe system 9 so that the concentration is 1% by weight with respect to carbon dioxide gas
/cd of supercritical carbon dioxide gas was passed through the pressure vessel 4 for 3 minutes.

The supercritical carbon dioxide gas flowing out from the pressure container is depressurized to 50 kg/- by a pressure reducing valve 5, and pollutants such as stripping agent and photoresist film residue are separated in a separation tank 6, and the carbon dioxide gas is released outside the system. did.

The supply of the release agent was stopped, and then the silicon wafer in the pressure container 4 was cleaned for 5 minutes using only supercritical carbon dioxide gas. When this silicon wafer was taken out from the pressure container 4 and subjected to quality inspection, it was confirmed that no contaminants such as stripping agent or photoresist film residue remained on the silicon wafer.

[Brief explanation of drawings]

Fig. 1 shows an example of an apparatus configuration for carrying out the method of the present invention, and Fig. 2 shows another example of the equipment configuration for carrying out the method of the present invention for circulating and reusing carbon dioxide gas. .

Claims (5)

[Claims] (1) The substrate on which the organic cured film is formed is immersed in an organic release agent to peel the organic cured film from the substrate, and then the substrate is brought into contact with liquefied gas or supercritical gas containing a subcritical state. . A method for removing an organic cured film, which comprises removing the above-mentioned release agent, peeling residue of the organic cured film, and other contaminants adhering to the substrate. (2) The method for removing an organic cured film according to claim 1, wherein the organic stripping agent contains an aromatic compound. (3) The method for removing an organic cured film according to claim 1, wherein the liquefied gas or the supercritical gas containing a subcritical state is carbon dioxide gas. (4) Claim 1, characterized in that the substrate is brought into contact with liquefied gas or supercritical gas containing a subcritical state for 2 to 15 minutes.
The method for removing an organic cured film described in . (5) The method for removing an organic cured film according to claim 1, wherein the substrate is a semiconductor wafer and the organic cured film is a photoresist film.