JPWO1998037575A1 - Surface treatment method and device - Google Patents

Abstract

(57) [Abstract] A heater (8) heats and vaporizes a processing liquid (6) inside a container (7), and the vapor is introduced into a processing chamber (1) via a pipeline (10) and regulated by a valve (9). A workpiece (5) is placed on a heating plate (4) set on a transport table (3) inside the processing chamber (1). The workpiece is heated by the heating plate so that its surface temperature is, for example, above the boiling point of the processing liquid. The surface of the workpiece is exposed to the processing liquid vapor introduced into the processing chamber, and depending on the type of processing liquid used, surface treatments such as surface modification (e.g., improving wettability), ashing, etching, and dry cleaning are performed. The effectiveness of the surface treatment can be enhanced by mixing an auxiliary gas with the processing liquid vapor and exposing the surface of the workpiece to this mixed gas. The processed workpiece is removed from the processing chamber by driving the transport table (3), and a new workpiece is then loaded and the surface treatment is repeated.

Description

Description: TECHNICAL FIELD The present invention relates to a surface treatment technique for etching or ashing the surface of a material to be treated to remove inorganic or organic substances, or for modifying the surface to improve wettability.

BACKGROUND ART With the advancement of semiconductor technology, various techniques have been developed for this type of surface treatment. For example, methods for removing organic matter from the surface of a substrate or other workpiece include wet cleaning using organic solvents and dry cleaning, which removes organic matter by irradiating it with ozone or ultraviolet light to induce a chemical reaction.

However, the above-mentioned wet cleaning method requires, in addition to the process of performing the desired treatment, a rinsing process to remove the treatment solvent and a process to dry the substrate. Furthermore, these additional processes require fixed equipment, which increases manufacturing costs.

Furthermore, conventional dry cleaning methods have limited ability to remove large-molecular-weight organic materials, making them ineffective for cleaning. To address this issue, methods have been developed that use plasma generated in a vacuum to remove organic or inorganic materials, or to perform etching or ashing. However, these methods require specialized equipment, such as a vacuum chamber and vacuum pump, making the overall facility complex and expensive, resulting in high costs. Furthermore, the time required to reduce pressure for discharge limits throughput. As a result, single-wafer processing is difficult, making in-line processing impossible.

In response to this problem, methods are known, such as those disclosed in Japanese Patent Application Laid-Open Nos. 2-281734, 3-236475, 5-23579, and 5-275190, in which plasma is generated by glow discharge at near-atmospheric pressure to uniformly or locally treat a large area of a workpiece, thereby performing surface modification such as etching, ashing, thin film formation, and hydrophilization. While this method does not require a vacuum device, it has problems such as complex discharge control and electrode devices for generating stable plasma.

The present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to provide a novel surface treatment method that does not require additional wet-treatment rinsing or drying steps, nor does it require expensive, large-scale equipment for vacuum or pressure reduction. It allows for a simple and compact device configuration, and enables surface treatments such as surface modification (e.g., improving wettability) and ashing and etching to be performed relatively easily and at low cost.

Another object of the present invention is to provide a novel apparatus for carrying out such a surface treatment method.

DISCLOSURE OF THE INVENTION According to one aspect of the present invention, there is provided a surface treatment method comprising heating a treatment liquid to generate vapor, and exposing the surface of a heated object to the vapor.

Because the surface of the workpiece is treated dry with the vapor of the treatment solution, various surface treatments, such as surface modification (e.g., improving wettability), etching, ashing, and dry cleaning, can be effectively performed in a wide range of fields by appropriately selecting the solution used, regardless of the shape or material of the workpiece. Furthermore, since no additional post-treatment steps, such as rinsing and drying, required for typical wet treatments, or the large vacuum equipment required for conventional dry treatments, are required, handling of the treatment solution and workpiece and the treatment process are relatively simple. The required equipment and facilities can be simplified and downsized, significantly reducing processing costs. Furthermore, in-line treatment and on-site treatment can be easily performed.

Heating the workpiece so that its surface temperature is equal to or higher than the boiling point of the treatment liquid is advantageous because it prevents the treatment liquid from cooling and liquefying on the workpiece surface, allowing for effective surface treatment.

The entire surface of the workpiece can be treated by heating it entirely, or only the desired areas can be selectively treated by heating only a portion of the surface.

Furthermore, by placing the workpiece in an atmosphere containing the vapor of the treatment liquid, the surface of the workpiece can be easily exposed to the vapor, thereby performing the desired surface treatment.

According to one embodiment, the treatment liquid is pure water, acidic water, or alkaline water, and the surface of the workpiece can be modified by exposing it to its vapor to improve its wettability or to ash the surface.

According to another embodiment, the processing liquid may be an acid, and the surface of the workpiece may be etched by exposure to its vapor. In another embodiment, the processing liquid may be an organic solvent, and the wettability of the surface of the workpiece may be improved. In yet another embodiment, the processing liquid may be an oxidizing liquid, and the surface of the workpiece may be ashed.

Furthermore, according to the present invention, an auxiliary gas can be mixed with the vapor of the treatment liquid, and the surface of the heated workpiece can be exposed to the mixed gas, thereby enabling the desired surface treatment to be carried out more effectively.

According to one embodiment, pure water, acidic water, or alkaline water is used as the processing liquid, and an oxidizing gas is used as the auxiliary gas. By exposing the workpiece to a mixed gas of the vapor of the processing liquid and the oxidizing gas, the wettability of the surface of the workpiece can be improved.

According to another embodiment, by using an oxidizing liquid as the treatment liquid and an oxidizing gas as the auxiliary gas, the surface of the workpiece can be oxidized or the wettability of the surface of the workpiece can be improved.

In yet another embodiment, the wettability of the workpiece surface can be improved by using an organic solvent as the treatment liquid and a non-oxidizing gas as the auxiliary gas.

The present invention also provides a surface treatment method that includes two or more ashing steps for ashing the surface of a workpiece, with at least the final ashing step comprising heating a treatment liquid to generate vapor and exposing the heated surface of the workpiece to the vapor. This allows the surface of the workpiece to be first treated using a method with a high ashing rate, followed by dry treatment using vapor from an appropriately selected treatment liquid. This allows for relatively easy, efficient, and complete ashing of any organic residue remaining on the surface, resulting in improved overall ashing efficiency.

According to another aspect of the present invention, there is provided a surface treatment apparatus comprising a steam generator that heats a treatment liquid to generate steam, and a heating device that heats a workpiece, wherein the surface of the heated workpiece is exposed to the steam. This facilitates the implementation of the surface treatment method of the present invention.

The surface treatment apparatus may advantageously further include a housing defining an atmosphere containing the vapor of the treatment liquid, and the surface of the treatment object may be easily exposed to the vapor by placing the treatment object in the housing.

The heating device can be a heating plate on which the workpieces are placed, thereby directly heating the workpieces. In another embodiment, the heating device can be a hot air blower for blowing hot air onto the surface of the workpieces, thereby allowing multiple workpieces to be heated substantially uniformly throughout and surface-treated simultaneously.

In another embodiment, a device for irradiating infrared or ultraviolet rays can be used as the heating device, and a mask for partially irradiating the surface of the workpiece with infrared or ultraviolet rays can be further provided, thereby enabling selective and localized surface treatment of desired portions.

In addition, according to the present invention, it is advantageous to further provide a gas supply device for supplying an auxiliary gas to be mixed with the vapor of the treatment liquid in order to more effectively perform the desired surface treatment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing the construction of a first embodiment of a surface treatment apparatus to which the present invention is applied.

FIG. 2 is a cross-sectional view showing a modification of the first embodiment.

FIG. 3 is a cross-sectional view showing another modified example of the first embodiment.

FIG. 4 is a schematic cross-sectional view showing the construction of a second embodiment of a surface treatment apparatus to which the present invention is applied.

FIG. 5 is a schematic cross-sectional view showing the construction of a third embodiment of a surface treatment apparatus to which the present invention is applied.

BEST MODE FOR CARRYING OUT THE INVENTION The structure of a first embodiment of a suitable apparatus for carrying out the surface treatment method of the present invention is shown schematically in Figure 1. This surface treatment apparatus comprises a housing 2 defining a treatment chamber 1 therein, in which a heating plate 4 set on a conveying table 3 is disposed, and an object to be treated 5 is placed thereon.

The housing 2 is connected to a steam generator comprising a container 7 containing a processing liquid 6 and a heater 8 for heating the container. The upper part of the container 7 is connected to the processing chamber 1 via a pipe 10 equipped with an inlet valve 9. The housing is also connected to the outside via an exhaust valve 11.

Depending on the desired surface treatment, various liquids can be used for the treatment liquid 6, such as water (including pure water and tap water), acidic water, alkaline water, oxidizing liquid, organic solvent, and acid. Specifically, considering ease of handling and environmental impact, water is the most preferable treatment liquid, but other liquids such as hydrogen peroxide, ethyl alcohol, and hydrogen fluoride can also be used.

The processing liquid 6 in the container 7 is heated and evaporated by a heater 8, and the resulting vapor is sent into the processing chamber 1 via a pipeline 10. The workpiece 5 in the processing chamber 1 is heated to an appropriate temperature by a heating plate 4. The exposed surface of the workpiece is exposed to the vapor of the processing liquid 6 introduced into the processing chamber 1, thereby performing the desired surface treatment. The processed workpiece 5 is removed from the processing chamber 1 by driving the transport table 3, and a new workpiece is then brought in, and the above surface treatment process is repeated.

The amount of steam inside the processing chamber 1 is controlled by adjusting the amount of steam supplied via the inlet valve 9 and the amount of steam exhausted via the exhaust valve 11, depending on processing conditions such as the volume of the processing chamber, how the workpiece is placed, and the type and speed of surface treatment.

The temperature of the heating plate is adjusted so that the vapor of the treatment liquid 6 does not liquefy on the surface of the workpiece 5. For example, if the surface temperature of the workpiece 5 is heated to a temperature above the boiling point of the treatment liquid, liquefaction can be reliably prevented. Furthermore, to achieve good surface treatment, it is preferable that the vapor in the treatment chamber 1 maintain its vapor phase at least during the surface treatment and that it is cooled by the inner surface of the housing 2 to prevent liquefaction. Therefore, it is advantageous to provide a separate heating means or to use the heating plate or heater to heat the housing 2 itself, which increases the efficiency of the surface treatment.

Furthermore, in order to efficiently perform the surface treatment of the present invention, it is effective to make the housing 2 as small as possible to reduce the volume of the treatment chamber 1, and to position the workpiece higher within the treatment chamber.

Experiments were conducted using the surface treatment apparatus of FIG. 1 and various types of liquid as treatment liquid 6, and the following results were obtained.

(Example 1) Pure water was used as the treatment liquid 6, and water vapor was generated and introduced into the treatment chamber 1. A thin aluminum oxide plate was placed on the heating plate 4 as the treatment object 5, and treatment was performed for 5 minutes at a surface temperature of approximately 200°C. The contact angle of the aluminum oxide plate surface was measured using a contact angle meter. It was 64° before treatment, but after treatment it was 6°, demonstrating improved water wettability.

Furthermore, when a similar experiment was performed using ethyl alcohol as the treatment solution 6, it was possible to similarly modify the surface of the aluminum oxide thin plate to improve its wettability.

(Example 2) As in Example 1, pure water was used as the treatment liquid 6, and water vapor was generated and introduced into the treatment chamber 1. A silicon plate coated with organic resist was placed on the heating plate 4 as the workpiece 5, and the resist plate was heated to a surface temperature of approximately 200°C and treated for 10 minutes. As a result, the resist was successfully removed from the silicon plate surface.

Furthermore, when a similar experiment was conducted using hydrogen peroxide as the treatment solution 6, ashing to remove the resist from the silicon plate was also successfully performed.

(Example 3) Hydrogen fluoride was used as the treatment liquid 6, and its vapor was generated and introduced into the treatment chamber 1. A quartz plate was placed on the heating table 4 as the workpiece 5, and the surface temperature was raised to 100°C and the treatment was carried out for 60 minutes. As a result, the surface of the quartz plate was successfully etched.

FIG. 2 shows a schematic structure of a modified example of the surface treatment device of FIG.

In this modification, instead of a heating plate, a hot air blower 12 is provided at the top of the treatment chamber 1 to blow hot air downward as a means for heating the treatment object 5.

A plurality of plate-shaped workpieces 5 are arranged vertically on a mounting base 13 on the conveyor table 3 so that they can be easily exposed to hot air. By using the hot air blower 12 in this manner, the plurality of workpieces 5 and the entire interior of the treatment chamber 1 can be heated almost uniformly, which is advantageous for batch treatment.

Furthermore, using the surface treatment device shown in Figure 2, experiments were conducted on the surface treatments of wettability improvement, ashing, and etching, similar to those in Examples 1 to 3, and similarly favorable results were obtained.

Figure 3 shows a schematic diagram of the structure of another modified example of the surface treatment apparatus of Figure 1. In this modification, instead of a heating plate, an infrared irradiation device 14, such as an infrared lamp with a reflector, is provided facing downward in the upper part of the treatment chamber 1 as a means for heating the workpiece 5. A mask 15 having an opening corresponding to the desired treatment portion of the workpiece 5 is placed directly above the plate-shaped workpiece 5 placed horizontally on the conveyor table 3.

In this manner, while irradiating the object with infrared rays so that only the desired treatment portion is heated, vapor of the treatment liquid 6 is introduced from the vapor generator into the treatment chamber 1. The entire exposed surface of the object 5 is exposed to the vapor, but the desired surface treatment is performed locally only on the heated treatment portion.

Other thermal radiation devices, such as ultraviolet radiation devices, may be used in place of the infrared radiation device 14. Ultraviolet radiation devices have the advantage that the temperature difference between the irradiated and unirradiated areas is greater than that of infrared radiation devices, allowing for more precise localized surface treatment.

Using the surface treatment apparatus of FIG. 3, experiments similar to those in Examples 1 to 3 were carried out, and similarly favorable results were obtained for each of the surface treatments of wettability improvement, ashing, and etching only on the portion of the object to be treated selected by the mask 15.

4 is a schematic diagram showing the structure of a second embodiment of a surface treatment apparatus according to the present invention. This surface treatment apparatus differs from the first embodiment shown in FIG. 1 in that a gas inlet 16 is provided branching off from the pipe 10, and by adjusting a valve 17, a selected gas can be supplied from the outside as an auxiliary gas, which can be mixed with the vapor of the treatment liquid 6 and introduced into the treatment chamber 1.

According to this embodiment, the desired surface treatment can be performed more effectively by appropriately combining the treatment liquid 6 and the auxiliary gas and exposing the heated workpiece to the gas mixture. The various liquid types described in the first embodiment above can be used as the treatment liquid. An oxidizing or non-oxidizing gas can be selected as the auxiliary gas depending on the purpose of the treatment.

For example, wettability can be improved by combining water or hydrogen peroxide with oxygen gas, or by combining hydrogen peroxide or ethyl alcohol with nitrogen gas. Ashing can also be performed by combining hydrogen peroxide with oxygen gas or nitrogen gas. Furthermore, the ashing effect can be enhanced by using ozone as an auxiliary gas.

Experiments were conducted using the surface treatment apparatus of FIG. 4 with several combinations of treatment solution 6 and auxiliary gas, and the following results were obtained.

(Example 4) Pure water was used as the treatment liquid 6, and oxygen gas was used as the auxiliary gas. A mixture of these gases was introduced into the treatment chamber 1. A thin aluminum oxide plate was placed on the heating plate 4 as the workpiece 5, and the surface was treated by exposing it to the mixed gas. This improved the wettability of the aluminum oxide plate surface.

Furthermore, when the same experiment was carried out using oxygen gas instead of hydrogen peroxide solution as treatment solution 6, it was possible to similarly perform surface modification that improved wettability.

Furthermore, when a similar experiment was performed using ethyl alcohol as the treatment liquid 6 and nitrogen gas as the auxiliary gas, the wettability was also improved.

(Example 5) A hydrogen peroxide solution was used as the treatment liquid 6, and oxygen gas was used as the auxiliary gas. A mixed gas of these was introduced into the treatment chamber 1. A silicon plate coated with an organic resist was placed on the heating plate 4 as the workpiece 5, and surface treatment was performed. As a result, the resist was removed from the silicon plate surface, allowing ashing to be performed.

FIG. 5 shows a schematic diagram of the structure of a third embodiment of a surface treatment apparatus according to the present invention. This surface treatment apparatus differs from the first and second embodiments in that a container 7 containing a treatment liquid 6 is placed on a heating plate 4 within the treatment chamber 1, and a gas inlet 16 for supplying a selected gas from outside is directly connected to the housing 2. This configuration allows the vapor of the treatment liquid 6 to be generated directly within the treatment chamber 1, eliminating the risk of the vapor being cooled while passing through the conduit 10, as in the first and second embodiments, and thus enabling more efficient surface treatment.

The present invention has been described in detail above using preferred embodiments. However, the gist of the present invention is that a desired surface treatment is achieved using relatively simple steps and equipment by evaporating a treatment solution and exposing the resulting vapor to a heated workpiece. In addition to the above-described embodiments, various modifications and variations can be made to the present invention.

For example, by spraying vapor of the treatment liquid using a nozzle equipped with a heater to prevent liquefaction, desired portions of the workpiece can be locally surface-treated. Furthermore, the heating device shown in Figures 2 and 3 can be used in place of the heating plate 5 in the surface treatment apparatus of the second or third embodiment.

Furthermore, especially when a large amount of organic matter to be removed adheres to the surface of the workpiece, it is preferable to perform two or more ashing steps. In this case, a method with a high ashing rate is used in the first ashing step to remove most of the organic matter in a short time, and by employing one of the surface treatment methods of the present invention described above in at least the final ashing step, any remaining organic residue can be completely removed from the surface of the workpiece. This allows the surface of the workpiece to be completely ashed relatively easily and efficiently overall.

Also, by changing the treatment solution during the surface treatment process according to the present invention, different surface treatments can be performed successively on the same object.Furthermore, by changing the mask in the apparatus of Figure 2, the same or different surface treatments can be performed successively on different portions of the same object.

───────────────────────────────────────────────────── (Note) This publication is based on the publication published internationally by the International Bureau of Patents (WIPO). The effect of the international publication of the Japanese patent application (Japanese utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (23)

[Claims] 1. A surface treatment method comprising heating a treatment solution to generate steam and exposing the surface of a heated workpiece to the steam. 2. The surface treatment method according to claim 1, wherein the object to be treated is heated so that the temperature of the surface thereof is equal to or higher than the boiling point of the treatment liquid. 3. The surface treatment method according to claim 2, wherein the entire surface of the workpiece is heated. 4. The surface treatment method according to claim 2, wherein the surface of the workpiece is heated only partially. 5. The surface treatment method according to any one of claims 1 to 4, wherein the object to be treated is placed in an atmosphere containing vapor of the treatment liquid. 6. The surface treatment method according to any one of claims 1 to 5, wherein the treatment liquid is pure water, acidic water, or alkaline water, and improves the wettability of the surface of the workpiece. 7. The surface treatment method according to any one of claims 1 to 5, wherein the treatment liquid is pure water, acidic water, or alkaline water, and the surface of the workpiece is ashed. 8. The surface treatment method according to any one of claims 1 to 5, wherein the treatment liquid is an acid and etches the surface of the workpiece. 9. The surface treatment method according to any one of claims 1 to 5, wherein the treatment liquid is an organic solvent, and improves the wettability of the surface of the workpiece. 10. The surface treatment method according to any one of claims 1 to 5, wherein the treatment liquid is an oxidizing liquid, and the surface of the workpiece is ashed. 11. The surface treatment method according to any one of claims 1 to 4, characterized in that an auxiliary gas is mixed with the vapor of the treatment liquid, and the surface of the heated object to be treated is exposed to the mixed gas. 12. The surface treatment method according to claim 11, wherein the treatment liquid is pure water, acidic water, or alkaline water, and the auxiliary gas is an oxidizing gas, thereby improving the wettability of the surface of the workpiece. 13. The surface treatment method according to claim 11, wherein the treatment liquid is an oxidizing liquid, and the auxiliary gas is an oxidizing gas, and the surface of the workpiece is oxidized. 14. The surface treatment method according to claim 11, wherein the treatment liquid is an oxidizing liquid and the auxiliary gas is an oxidizing gas, thereby improving the wettability of the surface of the workpiece. 15. The surface treatment method according to claim 11, wherein the treatment liquid is an organic solvent and the auxiliary gas is a non-oxidizing gas, thereby improving the wettability of the surface of the workpiece. 16. A surface treatment method comprising two or more ashing steps for ashing the surface of the workpiece, wherein at least the last ashing step is the method of claim 1. 17. A surface treatment device comprising a steam generator that heats a treatment liquid to generate steam, and a heating device that heats an object to be treated, wherein the surface of the heated object to be treated is exposed to the steam. 18. The surface treatment apparatus according to claim 17, further comprising a housing defining an atmosphere containing the vapor of the treatment liquid, the object to be treated being disposed within the housing. 19. The surface treatment apparatus according to claim 17 or 18, wherein the heating device is a heating plate on which the workpiece is placed. 20. The surface treatment apparatus according to claim 17 or 18, wherein the heating device is a hot air blower for blowing hot air onto the surface of the workpiece. 21. The surface treatment apparatus according to claim 17 or 18, wherein the heating device is a device that irradiates infrared rays or ultraviolet rays. 22. The surface treatment apparatus according to claim 21, further comprising a mask for partially irradiating the surface of the workpiece with infrared or ultraviolet light. 23. The surface treatment apparatus according to any one of claims 17 to 22, further comprising a gas supply device for supplying an auxiliary gas to be mixed with the vapor of the treatment liquid.