JPH04302145A - Cleaning method - Google Patents

Abstract

PURPOSE:To improve the ashing removal performance of an organic matter such as resist used as a mask for augmenting the throughput by a method wherein steam is sufficiently mixed with the ozone at a specific volume ratio, and the mixture is fed onto the surface of the object to be processed. CONSTITUTION:The ozone produced by an ozone producer 1 is led in a steam feed vessel 3 through an A-piping 2. This steam feed vessel 3 is fed with pure water or hydrogen peroxide by a constant quantity feeder 4 with a heater A5 built therein to maintain the constant water temperature inside the vessel 3. This steam 6 evaporated from the water in the vessel 3 are carried by the ozone stream 7 is fed to multiple gas feed nozzles 9. At this time, the volume of the steam 6 added to the ozone is specified to exceed about 0.7 times of the ozone volume, and they are sufficiently mixed. Through these procedures, the removing rate can be accelerated up to the level exceeding 120% compared with the case not fed with the steam.

Description

[Detailed description of the invention]

The present invention relates to a method for cleaning glass or silicon wafers and cleaning and removing organic substances such as photoresist used as a mask by converting them into a gas.

0002

INDUSTRIAL APPLICATION FIELD The method of the present invention is used for cleaning optical glass and liquid crystal glass, removing organic stains from processed surfaces in semiconductor device manufacturing, etc., and removing resist after use as a mask.

0003

BACKGROUND OF THE INVENTION The ashing and removal of organic substances using active oxygen atoms produced by the decomposition of ozone has been known for a long time, as disclosed in, for example, Japanese Patent Laid-Open No. 15939/1983.

[0004] In recent years, the cleaning or organic matter removal treatment temperature has been
Lower temperatures are desired. That is, even in ultra-fine semiconductor devices, it is essential to lower the processing temperature in order to prevent damage to liquid crystal substrates and the like using chromium films. However, in the ashing treatment method for organic matter that utilizes active oxygen atoms produced by the decomposition of ozone, there are strong temperature restrictions on its performance, such as the removal rate of resist films after they are used as masks in the manufacturing process of semiconductor devices. As the processing temperature decreases from 300°C to 250°C to 200°C, it decreases to approximately one-half or one-fourth. Under such circumstances, as a method for improving removal performance in low-temperature treatment, it is known to supply water together with ozone, as shown in Japanese Patent Publication No. 1-179329, for example. However, in the above-mentioned known examples, no consideration is given to the effect of increasing the amount of steam supplied. In addition, when supplying water vapor together with ozone by simply passing ozone into the aquarium, consideration must be given to the fact that the latent heat of vaporization of the water is taken away from the water, lowering the water temperature and reducing the amount of water vapor, and that the ozone gas is being cooled. It wasn't. In particular, in low-temperature processing, there is a problem in that the surface of the object to be treated is partially cooled, resulting in a reduction in the removal rate and a large non-uniformity in the removal rate distribution.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the removal performance by keeping the amount of water supplied above a certain value. In other words, by always supplying a constant amount of water and by preventing large differences in temperature distribution on the surface of the workpiece due to cooling of the supplied gas, removal performance can be improved, especially in low-temperature processing. be.

[0006]

[Means for Solving the Problems] The amount of water added to ozone is approximately 0.7 times or more the volume of ozone, and the water is sufficiently mixed with the ozone before being supplied to the surface of the object to be treated.

[0007] Raw material oxygen is passed through an ozone generator to generate ozone by electric discharge, and the ozone is introduced into a steam generating container. The amount of heat necessary to evaporate the amount of supplied water is supplied to the steam generating container from the outside. This evaporated water vapor is placed on an ozone stream, thoroughly mixed, and then supplied to the surface of the object to be treated. Insulate the piping until it is supplied to the surface of the object to be treated so that the steam emitted from the steam generating container does not condense on the way.

[0008]

[Operation] Ozone absorbs ultraviolet light of 254 nm and decomposes to produce active oxygen atoms in a high energy state. Addition of water seems to have the effect of increasing the quantum efficiency of active oxygen atom generation. The active oxygen atoms react with organic substances and are converted into gases such as CO2 and H2O, which are vaporized and removed. In addition, ultraviolet rays of 254 nm and 185 nm have the effect of breaking the chemical bonds of organic substances and have the effect of making the above reaction more likely to occur. The heat at the treatment temperature has the function of thermally decomposing ozone and promoting the reaction.

[0009] Since the supplied water vapor already has latent heat of evaporation, it does not remove the latent heat of evaporation from the object to be treated, thereby preventing the temperature of the object to be excessively lowered. Further, ozone is also deprived of its latent heat of vaporization and is not cooled by the cold water, so that the surface temperature distribution of the object to be treated is not excessively disturbed and the treatment speed distribution is not increased, so that uniform treatment can be achieved. .

0010

[Example] As a method for removing a resist film after being used as a mask on a wafer in the manufacture of semiconductor devices, ultraviolet rays and ozone are applied to the resist at atmospheric pressure to remove organic resist such as CO2, H2O, etc. An example of decomposing and removing the gas into gas will be explained. FIG. 1 is a conceptual diagram of an apparatus for explaining the above embodiment.

[0011] Raw material oxygen gas is made to flow through a narrow space between two quartz cylinders, and is discharged between the two cylinders to generate ozone by the ozone generator 1. The ozone is introduced into the steam supply tank 3 through the A pipe 2. Pure water or hydrogen peroxide is supplied to the water vapor supply tank by a quantitative replenishment device 4, and the water vapor supply tank 4 has a built-in heater A5 to keep the internal water temperature constant. The water vapor 6 evaporated from the water surface of the water vapor supply tank 4 rides on the ozone airflow 7 introduced into the water vapor supply tank 4 and is supplied to the plurality of gas supply nozzles 9 through the B pipe 8. Said B piping 8
is maintained at a temperature at which the supplied water vapor does not condense.

The plurality of gas supply nozzles 9 are welded through a synthetic quartz flat plate 10, and each nozzle 9 is arranged so as to avoid the center of rotation and not on the same radius of rotation.

A low-pressure mercury discharge lamp 11 whose arc tube is a synthetic quartz tube that is bent on a flat surface so as to be able to irradiate a flat surface is arranged on the nozzle arrangement side of the synthetic quartz flat plate 10. The low-pressure mercury discharge lamp 11 is housed in an alumite-finished aluminum lamp house 12. Inert gas such as nitrogen gas is introduced into the lamp house 12 to prevent ozone from being generated around the arc tube.

The surface 13 (polished surface) of the synthetic quartz flat plate 10 opposite to the nozzle arrangement side is polished to a precise flatness. A stage 14 with a built-in heater that can rotate and move up and down is arranged in front of the precision polishing surface 13. The wafer mounting portion of the stage 14 is a thin flat plate 15 made of quartz.
is arranged to avoid direct contact between the wafer and the metal stage 14. In order to improve the adhesion of the wafer to the stage, the wafer is vacuum-adsorbed via the thin flat plate 15 made of quartz.

The loading and unloading of the wafer 21 onto the stage 14 is performed by a transport robot (not shown) through an openable and closable transport window 17 provided in one direction of the processing chamber 16 surrounding the stage. At this time, the stage is driven up and down so that the wafer suction surface of the robot enters the back surface of the wafer. In addition, in order to cause the reaction gas supplied from the plurality of gas supply nozzles to pass uniformly and at high speed over the wafer surface, and at the same time to effectively provide active oxygen atoms with a short lifetime to the wafer surface, the wafer surface and the The gas flow gap 22 through which the reactant gases flow between the precision surfaces of the quartz plates is controlled to be extremely small during the process. During processing, the wafer 21 is rotated by the rotation of the stage and can be irradiated with ultraviolet rays and supplied with reactive gas almost uniformly over its entire surface.

A duct 18 for exhausting remaining ozone is arranged in the processing chamber 16, and the remaining ozone is converted into oxygen by a decomposer 19 and released into the atmosphere together with air.

A 6-inch diameter silicon wafer coated with a positive resist (OFPR-800) using the above method was used as a sample, the processing temperature was 200°C, the gas flow gap was 0.2 mm, and ozone was applied at a volume ratio of 4.7%. FIG. 2 shows the results of resist removal experiments in which various amounts of water vapor were added to oxygen gas containing 10 l/min of oxygen gas.

[0018]

It has been found that the present invention increases the removal rate until the amount of water vapor added becomes approximately 1.5 times the volume of ozone. In the case of this example, the amount of water vapor is reduced to 0.7 of the volume of ozone compared to the case where no water vapor is supplied.
When the temperature was doubled, a removal rate of 120% or more was obtained, and a removal rate of 116% or more was obtained compared to the case where the steam supply water tank was not heated and the latent heat of vaporization was left as it was. Also,
Since the wafer is not cooled by water that has had its latent heat of vaporization removed, the temperature of the wafer surface will not be excessively cooled locally due to the supply of these reactive gases, allowing for uniform resist removal processing and improved throughput. It worked.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining one embodiment of the present invention.

[Fig. 2] Fig. 2 is a diagram showing the results of one example of the present invention.

[Explanation of symbols]

Claims (1)

[Claims] Claim 1: A cleaning method in which organic matter is decomposed and vaporized and removed by the action of ozone and ultraviolet rays, in which water in a gas state or hydrogen peroxide vapor is mixed with ozone to remove the A cleaning method characterized in that the pressure ratio of the steam to ozone is approximately 0.7 or more.