JP2003203902A - Ashing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of ashing during a semiconductor manufacturing process, without the need for using the low-pressure plasma method using a vacuum chamber, by which processing unevenness will not occur, even in a product having a complicated shape. <P>SOLUTION: In this method of ashing during a semiconductor manufacturing process, discharge plasma treatment is performed. The surface of a product to be treated is irradiated with UV light. Then, at least one of opposed surfaces of a pair of opposed electrodes is covered with a solid dielectric, under pressure close to the atmospheric pressure. Glow discharge plasma, obtained by introducing a treatment gas between the pair of electrodes and applying an electric field, is brought into contact with the UV-irradiated product. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ashing treatment method in a semiconductor manufacturing process, and more particularly to an ashing treatment method in which ultraviolet irradiation treatment and atmospheric pressure plasma treatment are combined.

[0002]

2. Description of the Related Art Conventionally, in an ashing process for removing a resist in a semiconductor manufacturing process, active oxygen molecules or ozone molecules generated by ultraviolet irradiation treatment or low pressure plasma treatment are used to chemically act a resist film which is an organic substance. It is performed by using a kind of combustion phenomenon that causes ashing.
However, in the case of processing with an ultraviolet lamp, when processing an object having a complicated shape, ozone generated by ultraviolet rays is unlikely to enter into details, which causes a problem that processing unevenness occurs. On the other hand, in the case of low-pressure plasma processing, stable discharge cannot be performed unless the pressure is reduced to some extent, so batch processing is performed in a vacuum chamber, a vacuum exhaust device etc. is required, and it takes a long time to process by batch method The treatment was of low productivity. As a method of solving such a problem, in order to shorten the time of one batch processing, the size of the vacuum chamber is reduced to reduce the size of each of the objects to be processed.
A method for processing a number of sheets, a method for processing a large number of sheets at the same time, etc. are being studied, but the equipment becomes more expensive,
When processing a large area substrate by such a method,
Since a large-capacity vacuum container and a large-output vacuum exhaust device are required, the surface treatment device has become more expensive. Further, conventionally, as the ashing treatment by the plasma treatment, there is a method using atmospheric pressure plasma using helium, as proposed in, for example, Japanese Patent Laid-Open No. 7-99182, but helium gas is used in the natural world. There is a problem that the amount of existence is extremely small and it is expensive and the running cost is heavy.

[0003]

SUMMARY OF THE INVENTION In view of the above problems, the present invention does not rely on the low pressure plasma method using a vacuum container for the ashing in the semiconductor manufacturing process, and causes uneven processing even for objects having a complicated shape. The aim is to provide a way not.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, after increasing the reactivity of the surface layer of the object to be processed by ultraviolet irradiation treatment, stable discharge was performed under atmospheric pressure conditions. By using a combination of discharge plasma processing that can realize the state, the advantages of each other can be brought out, and it is possible to perform fine processing that could not be done only by ultraviolet processing, and the processing speed is fast and accurate. Therefore, the present invention has been completed.

That is, the first invention of the present invention is, in the ashing method in the semiconductor manufacturing process, characterized in that after the surface of the object to be processed is irradiated with ultraviolet rays, glow discharge plasma processing is carried out under a pressure near atmospheric pressure. Ashing processing method.

According to a second aspect of the present invention, in the glow discharge plasma treatment, at least one opposing surface of a pair of opposing electrodes is coated with a solid dielectric under pressure near atmospheric pressure,
The ashing treatment method according to the first aspect of the invention, which is a treatment in which glow discharge plasma obtained by introducing a treatment gas between the pair of electrodes and applying an electric field is brought into contact with an object to be treated. .

The third invention of the present invention is the ashing treatment method according to the first or second invention, wherein the glow discharge plasma treatment is a method of sucking and removing the exhaust gas after the treatment. .

The fourth invention of the present invention is the ashing method according to any one of the first to third inventions, characterized in that the ultraviolet irradiation treatment and the glow discharge plasma treatment are carried out in one chamber. is there.

A fifth aspect of the present invention is characterized in that the ultraviolet irradiation treatment is carried out in the presence of a treatment gas.
4 is an ashing processing method according to any one of the inventions.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Ultraviolet irradiation treatment of an object to be treated according to the present invention is carried out by a conventionally known method. For example, using an exposure type device that uses a water-cooled ultra-high pressure mercury lamp that generates very little heat, an air-cooled high-pressure mercury lamp, and a metal halide lamp, turn on the lamp, and combine it with a large reflecting mirror to use the light. It is preferable to use an apparatus having a structure for increasing the energy distribution and improving the energy distribution in the ultraviolet irradiation area. The illuminance of ultraviolet rays is 8 to 25 mW /
It is preferably about cm ² .

In the present invention, the object to be processed is subjected to the atmospheric pressure plasma processing after the above ultraviolet irradiation processing. Means for bringing the plasma into contact with the transported object include, for example, (1)
A method of transporting an object to be processed into a discharge space of plasma generated between opposed electrodes to bring the plasma into contact with the object to be processed, and (2) plasma generated between opposed electrodes to the outside of the discharge space. There is a method (remote type) of bringing the object to be processed into contact so as to guide it.

As a concrete method of the above (1), for example, a method of transporting an object to be treated between electrodes while applying an electric field between parallel plate type electrodes covered with a solid dielectric to generate plasma. , A method of transporting an object to be processed using a roll-roll electrode coated with a solid dielectric, a method of processing while supplying gas in a shower shape by using an upper electrode having a large number of holes, and blowing to one electrode There is a method in which a container-shaped solid dielectric having a mouth nozzle is provided, and plasma is sprayed from the nozzle onto the object to be processed which is transported on another electrode.

As a concrete method of the above (2),
An electrode structure in which an electric field is applied between a pair of opposing electrodes such as a parallel plate type electrode and a coaxial cylindrical type electrode, and plasma generated by introducing a processing gas between the electrodes is blown out from a long nozzle, a cylindrical nozzle, etc. Hereinafter, it may be referred to as a remote source)), and is a preferable method that does not damage the object to be processed by an electric field or the like by a discharge plasma processing method of spraying the object to be processed conveyed to the outside of the discharge space. Further, in both of the above methods, the exhaust gas after the ashing process is collected together with the waste organic substances after the process from the exhaust gas suction port provided near the processing section.

Examples of the electrodes include those made of simple metals such as copper and aluminum, alloys such as stainless steel and brass, and intermetallic compounds. The shape of the electrodes is not particularly limited, but it is preferable to have a structure in which the distance between the opposing electrodes is constant in order to avoid generation of arc discharge due to electric field concentration. As an electrode structure that satisfies this condition,
For example, parallel plate type, cylinder facing plate type, sphere facing plate type,
Examples include a hyperbolic opposed flat plate type and a coaxial cylindrical type structure.

The distance between the electrodes depends on the thickness of the solid dielectric,
It is appropriately determined in consideration of the magnitude of the applied voltage, the purpose of utilizing plasma, etc., but is preferably 0.1 to 50 mm. If it is less than 0.1 mm, it may not be enough to install the electrodes with a space therebetween. If it exceeds 50 mm, it is difficult to generate uniform discharge plasma.

Further, in the electrode for generating plasma, the facing surface of at least one of the pair of electrodes is coated with a solid dielectric, and the electrode covered with the solid dielectric is in close contact with and in contact with the electrode. It is necessary to completely cover the opposing surface of. If there is a portion where the electrodes directly face each other without being covered with the solid dielectric, arc discharge easily occurs from there.

The solid dielectric may have a sheet shape or a film shape, and preferably has a thickness of 0.01 to 4 mm. If it is too thick, a high voltage may be required to generate discharge plasma, and if it is too thin, dielectric breakdown may occur when a voltage is applied and arc discharge may occur.

Examples of the material of the solid dielectric include plastics such as polytetrafluoroethylene and polyethylene terephthalate, glass, metal oxides such as silicon dioxide, aluminum oxide, zirconium dioxide and titanium dioxide, and double oxidation such as barium titanate. Things etc. are mentioned.

In particular, the relative dielectric constant under the environment of 25 ° C. is 1
If a solid dielectric material of 0 or more is used, a high density discharge plasma can be generated at a low voltage, and the processing efficiency is improved. The upper limit of the relative permittivity is not particularly limited, but as a practical material, about 18,500 is available and can be used in the present invention. A solid dielectric having a relative dielectric constant of 10 to 100 is particularly preferable. Specific examples of the solid dielectric having a relative dielectric constant of 10 or more include metal oxides such as zirconium dioxide and titanium dioxide, and complex oxides such as barium titanate.

In the plasma treatment of the present invention, an electric field of high frequency, pulse wave, microwave or the like is applied between the electrodes to generate plasma, but it is preferable to apply a pulsed electric field. An electric field having a fall time of 10 μs or less is preferable.
If it exceeds 10 μs, the discharge state easily shifts to an arc and becomes unstable, and it becomes difficult to maintain the high-density plasma state due to the pulsed electric field. Further, the shorter the rise time and the fall time are, the more efficiently the gas is ionized at the time of plasma generation, but it is actually difficult to realize a pulsed electric field having a rise time of less than 40 ns. It is more preferably 50 ns to 5 μs. Note that the rising time referred to here means the time when the voltage (absolute value) continuously increases, and the falling time means the time when the voltage (absolute value) continuously decreases.

The electric field strength of the pulse electric field is 10 to 10
It is preferably set to 00 kV / cm. If the electric field strength is less than 10 kV / cm, the treatment takes too long, and if it exceeds 1000 kV / cm, arc discharge is likely to occur.

The frequency of the pulsed electric field is 0.5 kHz.
The above is preferable. If it is less than 0.5 kHz, the plasma density is low and the treatment takes too long. The upper limit is not particularly limited, but is commonly used 13.56M
A high frequency band such as Hz or a test-use 500 MHz may be used. Considering the ease of matching with the load and the handling property, the frequency is preferably 500 kHz or less. By applying such a pulsed electric field, the processing speed can be greatly improved.

Further, one pulse duration in the above pulsed electric field is preferably 200 μs or less. If it exceeds 200 μs, arc discharge is likely to occur. Here, one pulse duration is ON, OF
It means the continuous ON time of one pulse in the pulse electric field composed of the repetition of F.

When the discharge plasma processing method of the present invention is used for normal pressure discharge plasma processing in which glow discharge plasma is generated under a pressure near atmospheric pressure, the effect can be sufficiently exhibited. Atmospheric pressure discharge plasma treatment requires a higher voltage than the treatment at low pressure, so the method of the present invention is advantageous.

Under the pressure near the atmospheric pressure is 1.333.
It refers to under a pressure of × 10 ^{4 to} 10.664 × 10 ⁴ Pa. Among them, the pressure adjustment is easy, and the device is simple.
The range of × 10 ^{4 to} 10.397 × 10 ⁴ Pa is preferable.
The time required for the discharge plasma treatment is appropriately determined depending on the magnitude of the applied voltage, the object to be treated, the mixed gas composition, and the like.

The treatment method of the present invention is preferably a method in which the ultraviolet irradiation treatment operation and the atmospheric pressure plasma treatment operation are carried out in one chamber. In particular, since both methods can perform the treatment under normal pressure, the ultraviolet irradiation device and the plasma processing device can be housed in one chamber, and the ultraviolet irradiation treatment and the atmospheric pressure plasma treatment can be performed continuously, so that the process is efficient. The above is also advantageous.

A specific example of performing the ashing process in the above-mentioned one chamber will be described with reference to the drawings. FIG. 1 is a schematic device diagram for explaining an example of a process of performing an ashing process on an object to be processed by a device in which an ultraviolet irradiation device and a plasma processing device are housed in a chamber. In FIG. 1, an ultraviolet irradiation processing apparatus 2 and a plasma processing apparatus 3 are sequentially provided in a chamber 1 so that an object 4 to be processed which is set on a transfer table 5 and transferred can be processed. In the chamber 1, the processing gas is introduced from the processing gas introduction tube 6 and can be recovered from the ultraviolet irradiation processing area through the glow discharge plasma processing area and the exhaust tube 7. The object 4 to be processed is transferred by the transfer table 5, the surface is first activated by the ultraviolet irradiation device 2 equipped with the ultraviolet lamp 21 and the reflecting mirror 22, and then is processed by the remote source 3 of the plasma processing device. It The remote source 3 introduces a processing gas into the discharge space between the electrode 32 and the electrode 33 to which an electric field is applied from the power supply 31 from the processing gas introduction port 34 to turn it into plasma, and from the plasma blowout port 35, the object to be treated after the ultraviolet irradiation treatment is performed. The surface of the body 4 is sprayed. The treated exhaust gas is recovered from the stack 7 together with the entire treated gas flow.

The ultraviolet irradiation treatment is carried out while the object to be processed is being conveyed, but it is preferable that the interval between the object to be processed conveyed from the lower end of the ultraviolet ray generating portion is 1 to 100 mm. If the distance from the lower end of the ultraviolet ray generating portion to the object to be processed is less than 1 mm, it becomes difficult to convey the object to be processed, and if it is 100 mm or more, the processing effect becomes low.

Further, the plasma treatment is carried out while conveying the object to be treated after the ultraviolet irradiation treatment, but the treatment is carried out with a distance of 1 to 10 mm from the object to be treated conveyed from the plasma outlet of the remote source. It is preferable to carry out. If the distance from the remote source to the object to be processed is less than 1 mm,
It becomes difficult to convey the object to be processed, and if it is 10 mm or more, the processing effect becomes low.

FIG. 2 is a schematic device diagram for explaining another example of the process of performing the ashing process of the object to be processed by the device in which the ultraviolet irradiation device and the plasma processing device are housed in the chamber. In FIG. 2, an ultraviolet irradiation processing apparatus 2 and a plasma processing apparatus 3 are sequentially provided in a chamber 1 so that an object 4 to be processed which is set on a transfer table 5 and transferred can be processed. In the chamber 1, the processing gas is introduced from the processing gas introduction tube 6 and can be recovered from the ultraviolet irradiation processing area through the glow discharge plasma processing area and the exhaust tube 7. The object 4 to be processed is transferred by the transfer table 5, the surface thereof is first activated by the ultraviolet irradiation device 2 including the ultraviolet lamp 21 and the reflecting mirror 22, and subsequently processed by the plasma processing device. The plasma processing apparatus has a power supply 31.
In the discharge space between the electrode 32 and the electrode 33 to which an electric field is applied, the processing gas flowing from the ultraviolet irradiation processing region is turned into plasma, and the surface of the object 4 to be processed after ultraviolet irradiation processing which is transported in the discharge space is transferred to the discharge space. To process. The treated exhaust gas is collected from the exhaust stack 7.

According to the method combining the ultraviolet irradiation treatment and the plasma treatment, the plasma treatment is performed after the reactivity of the surface of the object to be treated is increased by the ultraviolet irradiation.
It has a higher effect than the case where the treatment is continued by the ultraviolet irradiation alone or the plasma treatment alone. In particular, since the plasma treatment can be performed under normal pressure, both devices can be accommodated in one chamber, and the method can be easily performed in terms of steps.

Further, in the present invention, the process gas is introduced into one chamber and exhausted to create a flow of the process gas, and ultraviolet irradiation process and plasma process are performed in the process, so that the ashing process speed is increased. Has the effect of improving. In particular, the presence of the processing gas in the ultraviolet irradiation treatment area first causes the active species generated by the ultraviolet rays to be further activated in the next plasma discharge area, which is a feature that the ashing treatment can be efficiently performed.

Here, the carrier table 5 in FIGS.
Can change the degree of processing by using a material whose feed speed can be arbitrarily adjusted, and a cooling or heating mechanism can be added.

From the above characteristics, the treatment method of the present invention is effective for the ashing treatment of the surface of the object to be treated of the semiconductor element, but it is also very useful when used for descum treatment, desmear treatment, etc. of the residue. The surface treatment can be effectively performed. Further, it can be used for dry etching, improvement of adhesion of organic film, reduction of metal oxide, surface modification and the like.

As the processing gas in the ashing process of the present invention, a gas that generates oxygen radicals is used to promote the combustion phenomenon of ashing. Examples of radicals that contribute to the oxidation reaction include oxygen molecules, excited oxygen molecules, oxygen molecular ions, oxygen atoms, oxygen atom ions, excited ozone molecules, and ozone molecule ions. As a source for generating these, any oxygen-containing gas may be used, and in addition to oxygen, carbon monoxide, carbon dioxide, air, steam or the like can be used. Introducing a gas containing oxygen as described above into plasma is particularly effective in removing unnecessary resin by oxidation treatment. In addition, a fluorine-based gas can be added if necessary depending on the type of the removal material.

The processing gas of the present invention is preferably a gas containing 1 to 50% by volume of oxygen, whereby high density plasma can be generated and high speed processing can be performed. If the oxygen content is less than 1% by volume, high concentration plasma cannot be realized. Although the treatment can be performed even if the oxygen content exceeds 50% by volume, the effect is almost the same, and therefore the following diluent gas may be used in terms of economy and handling.

As the diluent gas, argon, neon, xenon, helium, nitrogen, dry air (the oxygen content when using air is a value including oxygen in the air), etc. can be used. These may be used alone or in admixture of two or more. Considering the balance between the treatment effect, economy and handleability, a treatment gas composed of oxygen and argon, nitrogen or air is preferable.

Conventionally, the treatment in the presence of helium has been carried out under a pressure near atmospheric pressure, but according to the method of applying an electric field near atmospheric pressure of the present invention, compared with helium. Stable treatment in inexpensive argon or nitrogen gas is possible, and high density plasma can be generated even when the oxygen content is particularly small.

The object to be ashed in the present invention includes a liquid crystal display substrate, a photomask, a glass substrate on which wiring is drawn with photoresist, and a silicon wafer substrate on which wiring is drawn with photoresist. Can be mentioned. The processing method of the present invention is very effective for ashing processing on these substrates.

In the ashing treatment, the treatment capacity can be improved by heating the temperature of the object to be treated to preferably 15 to 180 ° C, more preferably 90 to 150 ° C. The method for heating the object to be processed is not particularly limited as long as it can uniformly and quickly heat the object to be processed, but a sheet heater or the like can be preferably used.

In the atmospheric pressure discharge using the pulsed electric field of the present invention, it is possible to cause the discharge directly to the atmospheric pressure between the electrodes without depending on the gas species at all, and a more simplified electrode structure and discharge can be obtained. It is possible to realize high-speed processing with the atmospheric pressure plasma device and the processing method according to the procedure. Further, processing parameters such as cleaning rate can be adjusted by parameters such as pulse frequency, voltage, and electrode interval.

[0042]

EXAMPLES The present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1 Ashing treatment was performed using the apparatus shown in FIG. For the ultraviolet irradiation, an apparatus having an irradiation part of 300 mm × 500 mm for irradiating the ultraviolet ray with a secondary voltage of 700 V and a secondary current of 0.2 A was used, and was set so that the distance to the object to be treated was 5 mm. The plasma treatment has a water cooling function inside the electrode, and the surface is coated with alumina to a thickness of 1.0 mm, and SUS3 of 300 mm × 500 mm × thickness of 20 mm is used.
Using parallel plate electrodes made of 04, using a remote source installed at a distance of 1 mm, the distance from the object to be processed is 3 m.
It was installed so that it would be m. 2 μm on the surface as the object to be processed
A 10 mm-thick glass base material on which a thick resist was formed was used, and it was moved at a conveyance speed of 50 mm / min. Dry air was used for both systems as the processing gas introduced into the chamber and the processing gas introduced into the plasma processing apparatus, and a rising time of 5 μs and a voltage of 20 were applied between the electrodes of the plasma processing unit.
A pulsed electric field of kV _PP and frequency of 50 kHz was applied. As a result, the resist removal process is performed uniformly, and the resist removal rate is improved by 150% as compared with the case where only the ultraviolet irradiation process is performed under the same apparatus and processing conditions.
The resist removal rate was improved by 180% with respect to the processing ability as compared with the case of performing only the plasma processing. The resist removal rate is a value obtained by measuring the film thickness before and after the treatment with an optical film thickness meter and using the following equation. Resist removal rate (%) = (film thickness before treatment−film thickness after treatment) /
Film thickness before processing x 100

Example 2 Ashing processing was performed using the apparatus shown in FIG. purple
External irradiation is purple with a secondary voltage of 700V and a secondary current of 0.2A.
It has a 300mm x 500mm irradiation part that irradiates an outside line.
Using the device, set the distance to the object to be processed to 5 mm.
I put it. Plasma treatment has a water cooling function inside the electrode.
Then, the surface is coated with alumina to a thickness of 1.0 mm.
SUS3 with 100mm x 500mm x 20mm thickness
04 parallel plate electrodes are used,
The space was set to 20 mm. As the object to be processed, the surface
1mm thick silicon with 1μm thick resist formed on
The wafer is moved at a transfer speed of 250 mm / min.
Let Plasma processing using dry air as processing gas
Rise time 5μs, voltage 18k between electrodes
V _PPA pulsed electric field having a frequency of 5 kHz was applied. That conclusion
As a result, the resist removal process is performed uniformly, and the same equipment and process are used.
Than when only UV irradiation is applied
In terms of processing capacity, the resist removal rate improved by 250%,
The processing capacity is better than that when processing only Zuma processing.
Gist removal rate improved by 150%.

Comparative Example 1 In the apparatus shown in FIG. 1, the ultraviolet irradiation treatment was not carried out, and only the plasma treatment was scanned twice. As a result, the resist removal treatment was performed uniformly, but the resist removal rate was 60% of that in Example 1.

As can be seen from Comparative Example 1, the ashing treatment by combining the ultraviolet irradiation treatment and the atmospheric pressure plasma treatment of the present invention is not only the sum of the effects of the respective treatments but also the resist removal rate is synergistically improved. However, the excellent ashing effect is exhibited.

[0047]

According to the present invention, the ashing process used in the semiconductor manufacturing process can be processed under atmospheric pressure by combining the ultraviolet irradiation process and the atmospheric pressure plasma process. You can Therefore, it is a processing method with very good productivity. Furthermore, the processing can be inlined and speeded up. This makes it possible to shorten the processing time and reduce the cost.

[Brief description of drawings]

FIG. 1 is a diagram of a schematic processing apparatus illustrating an example of an ashing processing method of the present invention.

FIG. 2 is a diagram of a schematic processing apparatus for explaining another example of the ashing processing method of the present invention.

[Explanation of symbols]

1 chamber 2 UV irradiation processing device 3 Plasma processing device (remote source) 4 Object to be processed 5 carrier 6 gas introduction tube 7 exhaust stack 21 UV lamp 22 Reflector 31 power supply 32, 33 electrodes 34 Processing gas inlet 35 Plasma outlet

Claims (5)

[Claims] 1. A method for ashing treatment in a semiconductor manufacturing process, wherein after irradiating a surface of an object to be treated with ultraviolet rays,
An ashing treatment method characterized by performing glow discharge plasma treatment under a pressure near atmospheric pressure. 2. In the glow discharge plasma treatment, under a pressure near atmospheric pressure, at least one opposing surface of a pair of opposing electrodes is coated with a solid dielectric, and a treatment gas is introduced between the pair of electrodes to generate an electric field. The ashing treatment method according to claim 1, wherein the glow discharge plasma obtained by applying an electric field is a treatment for contacting the object to be treated. 3. The ashing treatment method according to claim 1, wherein the glow discharge plasma treatment is a method of sucking and removing the exhaust gas after the treatment. 4. The ashing treatment method according to claim 1, wherein the ultraviolet irradiation treatment and the glow discharge plasma treatment are performed in one chamber. 5. The ashing treatment method according to claim 1, wherein the ultraviolet irradiation treatment is performed in the presence of a treatment gas.