JP5267980B2 - Surface treatment method and apparatus using ozone gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means that improves oxidization efficiency in a surface treatment method by oxidization using both ozone gas and ultraviolet rays. <P>SOLUTION: Mixed gas of ozone gas and rare gas such as xenon gas is applied to a workpiece while the mixed gas is irradiated with ultraviolet light. The oxygen molecule density in the mixed gas is reduced so as to accelerate decomposition of ozone gas, thereby improving oxidization efficiency and allowing atomic oxygen to effectively reach the substrate surface. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a surface treatment technique resulting from oxidation, and more particularly to a surface treatment technique for forming an oxide film on the surface of an object to be processed in an oxidation reactive gas atmosphere or resist ashing the surface of the object to be processed.

  Conventionally, it is well known that the surface of an object to be processed such as a substrate is oxidized or resist ashed using the high oxidizing power of ozone. For example, in the case of oxidizing a silicon substrate, if it is attempted to oxidize with oxygen gas, the substrate temperature needs to be raised to 900 to 1000 ° C. or higher. However, when ozone gas is used, the substrate temperature is lowered by several hundred degrees. Can also be oxidized.

  In this case, since the oxidation reaction proceeds as the ozone concentration in the ozone gas increases, an apparatus for generating an ozone-oxygen mixed gas having an ozone concentration of 90 vol% or more has been developed.

  In addition, low-temperature oxidation in which the substrate temperature is further lowered using ozone gas has been applied. In this case, as the substrate temperature is lowered, the thermal decomposition rate of ozone on the surface of the substrate gradually decreases. Therefore, when the surface temperature becomes 500 ° C. or lower, the oxide film formation rate on the substrate surface is greatly decreased. Therefore, in order to compensate for the decrease in the ozonolysis rate due to thermal decomposition, it may be possible to perform the oxide film formation process even at a low temperature of 500 ° C. or lower by irradiating ozone gas with ultraviolet light having a wavelength for forcibly decomposing ozone. .

  In general, in the treatment using ozone gas, atomic oxygen (or oxygen radicals) generated by decomposing ozone contributes most effectively to the oxidation, and the oxidation proceeds as many atomic oxygens can reach the substrate surface. For that purpose, it is necessary to take a technique such as a) increasing the pressure of ozone gas, b) increasing the ozone concentration in the ozone gas, or c) increasing the ultraviolet intensity in the case of oxidation with ultraviolet light + ozone. There is.

  Atomic oxygen is highly reactive, but has the property of reacting with oxygen molecules to easily deactivate the oxygen. Therefore, in order to effectively use the reactivity of ozone gas, it is effective to reduce the density of oxygen molecules. In general, since ozone gas is supplied in the form of an ozone-oxygen mixed gas diluted with oxygen, it is effective to increase the ozone concentration.

  However, if the ozone gas has a higher ozone concentration and the gas pressure is higher than the boundary pressure, if the ozone gas begins to decompose excessively at some point where the ozone gas is filled, the decomposition propagates explosively throughout the ozone. There is a nature to do. The boundary pressure is, for example, about 1.5 kPa at an ozone concentration of 20 vol%.

Therefore, it is necessary to use high-concentration ozone gas in a reduced pressure region below this boundary pressure, or to reduce the ozone gas concentration in the ozone-oxygen mixed gas.
Furthermore, in order to effectively utilize the oxidation reactivity of ozone gas, it is necessary to effectively make atomic oxygen generated from ozone reach the substrate surface. For this purpose, the density of oxygen molecules must be reduced, Alternatively, it is necessary to bring the generation site of atomic oxygen close to the substrate.

  The present invention has been proposed in view of such a point, and an object thereof is to provide means capable of improving oxidation efficiency in an oxidation surface treatment method using ozone gas and ultraviolet rays in combination.

In order to achieve the above-mentioned object, the present invention uses a mixed gas of ozone gas and a rare gas as a processing gas, and the ozone gas constituting the processing gas is a high-concentration ozone gas having a mixing ratio of oxygen gas of 30 vol% or less, a rare gas mixture the concentration of the processing gas is 33 to 66%, characterized in that the process gas is applied to the object to be treated was a surface treatment by oxidation by irradiating action of ultraviolet light to be so that the mixture gas It is said.

In the present invention, a mixed gas of ozone gas and a rare gas is used as a processing gas, and the ozone gas constituting the processing gas is a high-concentration ozone gas having a mixing ratio of oxygen gas of 30 vol% or less, and the mixed concentration of the rare gas in the processing gas. 33-66%, this processing gas is applied to the object to be processed, and the mixed gas is irradiated with ultraviolet light, so that the oxidation efficiency is improved while reducing the oxygen molecular density in the mixed gas. It is possible to make it .

FIG. 1 is a schematic configuration diagram of an oxide film manufacturing apparatus showing an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of an oxide film forming chamber.
This oxide film manufacturing apparatus is a processing gas supply path for supplying a mixed gas of high-concentration ozone gas and xenon gas diluted with oxygen to a processing chamber (2) that contains and holds a work (1) for forming an oxide film on the surface. (3) and the processing gas discharge path (4) are connected in communication.

  The processing gas supply path (3) has an ozone-oxygen mixed gas path (6) connected to the ozone generator (5) and a rare gas path (8) connected to the xenon gas storage container (7). And connected to the processing chamber (2) via an inlet ozone concentration meter (9).

  In the processing gas discharge path (4), an outlet side ozone concentration meter (10), an ozonolysis device (11), and a vacuum pump (12) are arranged in this order from the processing chamber (2) side.

  The inside of the processing chamber (2) is partitioned by an infrared transmitting partition wall (13). The upper surface of the infrared transmitting partition wall (13) is formed on the mounting portion of the work (1) and the infrared transmitting partition wall (13 A heater (14) for heating the workpiece is arranged in the chamber space located below (). In addition, an ultraviolet transmissive window (15) is formed on the wall surface of the processing chamber (2) facing the workpiece mounting portion, and an ultraviolet light source (16) is arranged corresponding to the ultraviolet transmissive window (15). is there. A processing gas inlet (17) connected to the processing gas supply path (3) is connected to one side wall of the mounting portion forming space of the work (1) of the processing chamber (2), and a processing gas discharge path ( A processing gas outlet (18) to which 4) is connected is formed as an opening.

In FIG. 1, reference numeral (19) denotes an oxygen gas supply source that is connected to the ozone generator (5). The ozone generator (5) is an ozone concentrating means such as a PSA device and has an ozone concentration of 10 vol% or more. The high-concentration ozone gas can be generated and supplied. In addition, in FIG. 1, (20) is a flow regulator installed in the ozone-oxygen mixed gas path (6), (21) is a check valve interposed in the ozone-oxygen mixed gas path (6), and (22) is A flow regulator installed in the rare gas passage (8), (23) is a check valve interposed in the rare gas passage (8), and (24) is a pressure gauge that detects the internal pressure of the processing chamber (2). is there.

  In the oxide film manufacturing apparatus described above, the mixed gas is supplied into the processing chamber (2) in a state where the high-concentration ozone gas and the rare gas are mixed by adjusting the flow rate with the flow rate regulators (20) and (22). The mixed gas of the high-concentration ozone gas and the rare gas is allowed to act on the workpiece (1) such as a substrate disposed in the chamber (2) while irradiating with ultraviolet light.

  As the ultraviolet light source, a xenon-mercury lamp, a dielectric barrier discharge lamp, or a laser with a wavelength of 254 nm can be used. Further, the distance between the workpiece (1) such as a substrate and the ultraviolet ray transmitting window (15) is set to about 1 mm, but this distance may be further shortened.

  FIG. 3 shows a different embodiment of the present invention, which allows ultraviolet light to be incident parallel to the work (1) placed and fixed in the processing chamber (2), so that the work (1) can be rotated. A support base (25) is held, and the support base (25) is rotated during processing by the operation of the rotational drive source (26). In this case, the ultraviolet light beam has a sheet shape, and the distance between the workpiece (1) and the ultraviolet light beam surface is 1 mm. Since the workpiece (1) is rotating, an oxide film having a uniform thickness can be formed.

  Thus, when irradiating a workpiece | work (1) with ultraviolet light in parallel, since ultraviolet light passes in ozone-rare gas mixed gas, it is absorbed by ozone gas and the intensity | strength in the downstream becomes small. Therefore, high-intensity light may be supplied using a pulsed ultraviolet laser having a pulse width of picoseconds to nanoseconds. Further, ultraviolet light may be transmitted by decreasing the ozone density.

  In each of the above embodiments, xenon gas is used as a rare gas to be mixed with oxygen-diluted ozone gas. As the rare gas, in addition to the above xenon gas, helium gas, neon gas, argon gas, krypton gas are used. Can be used.

FIG. 4 shows the relationship between the total gas flow rate and the oxide film thickness when ozone gas is diluted with oxygen using ultraviolet irradiation and diluted with argon gas. In this case, ultraviolet rays, wavelength 254 nm, the ultraviolet intensity contained in the mercury-xenon lamp light, specifications on 31 mW / cm ^2, was used for 60 mW / cm ² in actual measurement values.

  FIG. 4A shows a case where a silicon substrate having a diameter of 50 mm and a thickness of 370 μm is used, oxygen gas or argon gas as a dilution gas is added at 100 sccm at a substrate temperature of 350 ° C. and an ozone flow rate of 100 sccm, and dilution gas. 3 shows the relationship between the formed silicon dioxide film thickness and the gas flow rate when 200 sccm of oxygen gas or argon gas is added.

  FIG. 4B shows a case where a silicon substrate having a diameter of 50 mm and a thickness of 370 μm is used, and oxygen gas or argon gas 145 sccm as a dilution gas is added at a substrate temperature of 450 ° C. and an ozone flow rate of 150 sccm. 3 shows the relationship between the formed silicon dioxide film thickness and the gas flow rate when 290 sccm of oxygen gas or argon gas is added.

FIG. 5 shows the relationship between the total gas flow rate and the oxide film thickness when ozone gas is diluted with oxygen using ultraviolet light irradiation and diluted with xenon gas. As with ultraviolet light forward type, wavelength 254 nm, the ultraviolet intensity contained in the mercury-xenon lamp light, specifications on 31 mW / cm ^2, was used for 60 mW / cm ² in actual measurement values.

  FIG. 5A shows a case where a silicon substrate having a diameter of 50 mm and a thickness of 370 μm is used, and oxygen gas or xenon gas 150 sccm as a dilution gas is added at a substrate temperature of 350 ° C. and an ozone flow rate of 150 sccm. 3 shows the relationship between the formed silicon dioxide film thickness and the gas flow rate when 290 sccm of oxygen gas or xenon gas is added.

  FIG. 5B shows a case where a silicon substrate having a diameter of 50 mm and a thickness of 370 μm is used, oxygen gas or xenon gas as a dilution gas is added at 150 sccm with a substrate temperature of 450 ° C. and an ozone flow rate of 300 sccm. The relationship between the formed silicon dioxide film thickness and the gas flow rate when oxygen gas or xenon gas as a gas is added at 300 sccm is shown.

  As a result, generally, when the flow rate increases, the cooling effect increases and the oxidation rate decreases (see the case of oxygen dilution), but such a tendency is not observed in the case of dilution with a rare gas.

FIG. 6 is a diagram showing changes in oxide film thickness depending on the presence or absence of ultraviolet irradiation. This figure shows the oxide film thickness with and without UV irradiation when forming an oxide film using 290 sccm of ozone gas with 5 vol% xenon gas added to a silicon substrate having a diameter of 50 mm and a thickness of 370 μm. Shows changes.
According to this figure, the oxide film thickness without ultraviolet light irradiation is about 1.6 nm, while with ultraviolet light irradiation, the oxide film thickness increases to 2.1 nm. .

FIG. 7 is a diagram showing the relationship between the ozone concentration and the ashing rate when the ozone-oxygen mixed gas to which xenon gas is added and ultraviolet irradiation are used in combination.
In this case, a 1 cm × 1 cm resist-coated wafer was placed in a chamber with an internal volume of 300 cc and irradiated with ultraviolet light having a wavelength of 254 nm. The processing conditions were a pressure of 27 Torr and a substrate temperature of 55 ° C.
FIG. 7 shows that even when the ozone concentration is the same, the ashing rate can be increased when diluted with xenon gas than when diluted with oxygen.

  FIG. 8 shows changes in the ashing rate when the amount of xenon added is changed while the ozone concentration is 15 vol% (remaining oxygen), the flow rate is 500 sccm (ozone 75 sccm + oxygen 425 sccm), the substrate temperature is 55 ° C., and the pressure is 27 Torr. . The resist applied to this wafer had a baking temperature of 180 ° C. and a film thickness of 1.2 μm. The ashing speed was obtained by dividing the resist film thickness before and after the treatment by the treatment time.

  As shown in FIG. 8A, the ashing rate was increased by about 30% just by adding 0.2% xenon gas and 1 sccm actual flow rate to the total flow rate. However, the ashing rate did not change much even when added at about 1% or more, and a tendency to saturate was observed. Furthermore, as shown in FIG. 8B, it was confirmed that a portion where the gas flow was large was selectively ashed.

  The oxygen gas component in the ozone-oxygen mixed gas to which the xenon gas used for the treatment is added is 30 vol% or less, preferably 10 vol% or less. In addition, when the workpiece is a silicon substrate, the processing temperature in the processing chamber can be from room temperature to 1200 ° C., preferably 500 ° C. or lower, more preferably 400 ° C. or lower. preferable.

  As the ultraviolet rays to be irradiated, light having a wavelength in the range of 200 to 300 nm can be used. The ultraviolet light may be a continuous wavelength, a plurality of wavelengths, or a single wavelength using a laser or the like. Further, the ultraviolet rays may be pulsed or continuously irradiated.

  The present invention can be used for an oxidation process such as an oxide film formation process or a resist ashing process in a semiconductor manufacturing department.

It is a schematic block diagram of the oxide film manufacturing apparatus which shows one Embodiment of this invention. It is a schematic block diagram of an oxide film formation chamber. It is a schematic block diagram of the oxide film formation chamber which shows different embodiment. It is a figure which shows the relationship between the total flow volume of gas, and the oxide film thickness in the case where the ozone gas is diluted with oxygen and the case where it is diluted with argon gas in combination with ultraviolet light irradiation. It is a figure which shows the relationship between the total flow rate of gas, and the oxide film thickness in the case where the ozone gas is diluted with oxygen in combination with ultraviolet light irradiation and the case where it is diluted with xenon gas. It is a figure which shows the change of the oxide film thickness by the presence or absence of ultraviolet light irradiation. It is a figure which shows the relationship between the ozone concentration and the ashing rate at the time of using together the ozone oxygen mixed gas which added xenon gas, and ultraviolet light irradiation. It is a figure which shows the change of the ashing rate at the time of changing the addition amount of the xenon gas added to ozone gas.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... To-be-processed object, 2 ... Processing chamber, 15 ... Ultraviolet transmission window, 16 ... Ultraviolet light source, 17 ... Mixed gas inlet, 18 ... Mixed gas outlet

Claims (10)

A surface treatment method for performing surface treatment due to oxidation using ozone gas,
A mixed gas of ozone gas and rare gas is used as the processing gas, and the ozone gas constituting the processing gas is a high-concentration ozone gas with a mixing ratio of oxygen gas of 30 vol% or less, and the mixed concentration of the rare gas in the processing gas is 33 to 66%. age,
A surface treatment method using ozone gas, wherein the treatment gas is allowed to act on the object to be treated, and the surface of the object to be treated is oxidized by irradiating the treatment gas with ultraviolet light.   The surface treatment method using ozone gas according to claim 1, wherein the surface treatment resulting from oxidation is silicon oxidation treatment.   The surface treatment method using ozone gas according to claim 1, wherein the surface treatment resulting from oxidation is a resist ashing treatment. The surface treatment method using ozone gas according to claim 1, wherein the rare gas is xenon.   The surface treatment method using ozone gas according to any one of claims 1 to 4, wherein the object to be treated is in a heated state.   A processing gas introduction port for introducing a processing gas into a processing gas that is a mixed gas of high-concentration ozone gas with a mixing ratio of oxygen gas of 30 vol% or less and a rare gas with a mixing concentration set to 33 to 66 vol% ( 17) and the process gas outlet (18) are disposed in the processing chamber (2) for accommodating the object to be processed, and an ultraviolet transmissive window (15) is disposed in the processing chamber (2). The ultraviolet light source (16) is positioned so as to correspond to the transmission window (15), and the surface of the object (1) accommodated in the processing chamber (2) is subjected to surface treatment caused by oxidation. Ozone gas surface treatment equipment.   The surface treatment apparatus using ozone gas according to claim 6, wherein the surface of the object to be treated (1) is oxidized by a mixed gas of high-concentration ozone gas and rare gas and ultraviolet light from an ultraviolet light source (16).   The surface treatment apparatus using ozone gas according to claim 6, wherein the surface of the object to be treated (1) is subjected to resist ashing treatment with a mixed gas of high-concentration ozone gas and rare gas and ultraviolet light from an ultraviolet light source (16). The surface treatment apparatus using ozone gas according to any one of claims 6 to 8, wherein the rare gas is xenon.   The ozone gas utilization surface treatment apparatus of any one of Claims 6-9 equipped with the heating means (14) which heats the to-be-processed object in a process chamber.

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