JP4113438B2 - Resist stripping method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resist stripping method and a resist stripping apparatus for stripping a resist formed on a substrate (including a base material) in a semiconductor manufacturing process or the like.
[0002]
[Prior art]
In semiconductor manufacturing processes such as LSI and liquid crystal display manufacturing and manufacturing processes of multilayer printed wiring boards and the like, various resists such as photosensitive resins are used for pattern formation depending on the purpose. These resists are removed (peeled) in a step after pattern formation.
[0003]
As a resist stripping method, a wet process using a chemical solution or a process using low-pressure plasma is generally employed.
[0004]
By the way, in wet processing using a chemical solution, processing such as washing and drying of the chemical solution is required as a post process. Further, if the drying is insufficient, there is a problem that the remaining chemical causes poor quality.
[0005]
In addition, since the process using low-pressure plasma is a decompression process, it takes a lot of time for evacuation, and there is a problem that throughput is poor. Furthermore, when processing a large-area substrate, a large-capacity vacuum vessel / evacuation apparatus is required, which increases the cost of the apparatus.
[0006]
In view of this, a method has been proposed in which plasma is generated near atmospheric pressure for processing. For example, an inert and stable halogen-based gas is supplied to the discharge unit, and a reactive gas is generated by generating a discharge under a pressure near atmospheric pressure, and the reactive gas is guided to a resist substrate in the processing chamber. A method for removing the resist on the substrate has been proposed (for example, see Patent Document 1). Note that a substrate (including a base material) on which a resist is formed is called a resist substrate.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-58505
[Problems to be solved by the invention]
By the way, in the method described in Patent Document 1 (Japanese Patent Laid-Open No. 2000-58505), since halogen gas and H ₂ O are converted into plasma at the discharge portion of the discharge unit at one time, reaction of HF or the like at the discharge portion. Gas is generated and the discharge electrode of the discharge unit deteriorates. Therefore, it is necessary to devise an electrode material, and there is a problem that the cost increases.
[0009]
The present invention has been made in view of such circumstances, and it is possible to reduce damage to the discharge electrode for generating plasma when the resist on the substrate is peeled off by plasma processing under a pressure near atmospheric pressure. An object is to provide a resist stripping method and a resist stripping apparatus.
[0010]
[Means for Solving the Problems]
The stripping method of the present invention is a method for stripping a resist laminated on a substrate (including a base material) via a SiO ₂ layer, and is suitable for using a halogen-based gas that has been plasmatized under a pressure near atmospheric pressure. and generating an active reaction gas is introduced into the air with humidity by irradiating the active reaction gas to the substrate, etching the SiO ₂ layer active reaction gas is transmitted through the resist, and And a process of imparting a functional group to be hydrolyzed to the resist, and a process of decomposing the resist modified by the gas process by hydrolysis and lifting off the resist substantially peeled off by the etching. Yes.
[0011]
Patent does not charge peeling device of the present invention is an apparatus for removing the resist formed on the substrate (including a substrate), a plasma generator for generating plasma space under a pressure near atmospheric pressure, the plasma Gas treatment that has a gas supply source for supplying halogen-based gas to the space, introduces plasma-generated halogen-based gas into the atmosphere with appropriate humidity, generates active reaction gas, and irradiates the resist on the substrate And a decomposition treatment system for subjecting the resist gas-treated by the gas treatment system to hydrolysis treatment.
[0012]
In the present invention, the humidity of the atmosphere (the atmosphere around the plasma generating portion) into which the halogenated gas into plasma is introduced is 20% or more at room temperature, and the upper limit is a range in which no condensation occurs. A more preferable humidity range is about 40 to 60%.
[0013]
<Action>
In the present invention, the resist is removed by the following treatments (1) to (3).
[0014]
(1) An active reaction gas is generated by introducing a halogen-based gas that has been converted to plasma near atmospheric pressure into an atmosphere having an appropriate humidity.
[0015]
For example, when a halogenated gas such as CF ₄ or C ₂ F ₆ is ionized, CF ₁ to ₃ radicals (active reaction gas) are generated, and when these radicals are injected into the atmosphere, O ₂ and H _{2 in the} atmosphere are generated. by reacting with O COF ₂ is generated, also, HF is generated after the COF ₂ is reacted with H ₂ O.
[0016]
Here, as described above, if the halogen-based gas and H ₂ O are turned into plasma at the plasma generating portion at once, a reactive gas such as HF is generated and the electrode material is deteriorated. The cost becomes high. Therefore, in the present invention, deterioration of the electrode material is prevented by supplying only a dry halogen-based gas to the plasma generator (plasma space between the discharge electrodes). In addition, when activating a gas in the plasma generation unit, if a single gas (halogen-based gas only) is introduced into the plasma generation unit, the controllability of discharge can be improved rather than discharging all of the plurality of gases required for processing. There is also an advantage of getting better.
[0017]
(2) The resist substrate is irradiated with the active gas generated by the reaction in the atmosphere to etch the SiO ₂ layer under the resist (etching by passing the active gas through the resist) and to add a functional group to be hydrolyzed. Specifically, [—COF ₂ group] is introduced.
[0018]
(3) The gas-treated resist substrate is washed with pure water or the like to hydrolyze the modified resist. Specifically, [—COF ₂ ] is hydrolyzed (—COF ₂ + H ₂ O → COOH + HF), and the substantially stripped resist is removed by lift-off with pure water or the like.
[0019]
Next, the present invention will be described in more detail.
[0020]
In the present invention, the halogen-based gas is turned into plasma by a discharge plasma treatment under a pressure near atmospheric pressure. Under pressure near atmospheric pressure refers to a pressure condition of 1.333 × 10 ^{4 to} 10.664 × 10 ⁴ Pa. Among them, easy pressure adjustment, is preferably in the range of ^{9.331 × 10 4 ~10.397 × 10 4} Pa for device configuration is simplified.
[0021]
In the present invention, examples of the plasma generating unit that converts the halogen-based gas into plasma include an apparatus that generates glow discharge plasma by applying an electric field between the counter electrodes.
[0022]
Examples of the material of the electrode that generates plasma include simple metals such as iron, copper, and aluminum, alloys such as stainless steel and brass, and intermetallic compounds. The pair of electrodes constituting the counter electrode preferably has a structure in which the distance between the counter electrodes (plasma space) is constant in order to avoid occurrence of arc discharge due to electric field concentration. Specific examples of the electrode structure include a parallel plate type, a roll-plate type, a roll-roll type, and a coaxial cylindrical type structure.
[0023]
It is necessary to dispose a solid dielectric between the counter electrodes. Specifically, a solid dielectric may be disposed on at least one of the pair of electrodes constituting the counter electrode. At this time, it is preferable that the solid dielectric and the electrode on the side to be installed are in close contact with each other and the opposite surface of the electrode in contact is completely covered. If there is a portion where the electrodes directly face each other without being covered by the solid dielectric, arc discharge is likely to occur therefrom.
[0024]
The solid dielectric may be in the form of a sheet or a film. The thickness of the solid dielectric is preferably 0.01 to 4 mm. If the thickness of the solid dielectric is too thick, a high voltage may be required to generate discharge plasma, and if it is too thin, dielectric breakdown may occur during voltage application and arc discharge may occur. The solid dielectric may be a film coated on the electrode surface by a thermal spraying method.
[0025]
Examples of the solid dielectric include plastics such as polytetrafluoroethylene and polyethylene terephthalate, glass, metal dioxide such as silicon dioxide, aluminum oxide, zirconium dioxide, and titanium dioxide, and double oxides such as barium titanate. It is done.
[0026]
The solid dielectric preferably has a relative dielectric constant of 2 or more (25 ° C. environment, the same applies hereinafter). Specific examples of the solid dielectric having a relative dielectric constant of 2 or more include polytetrafluoroethylene, glass, and metal oxide film. Further, in order to stably generate a high density discharge plasma, it is preferable to use a solid dielectric having a relative dielectric constant of 10 or more. The upper limit of the relative dielectric constant is not particularly limited, but about 18,500 is known as an actual material. Examples of the solid dielectric having a relative dielectric constant of 10 or more include a metal oxide film mixed with 5 to 50% by weight of titanium oxide and 50 to 95% by weight of aluminum oxide, or a metal oxide containing zirconium oxide. The thing which consists of a material film can be mentioned.
[0027]
The distance between the electrodes of the counter electrode used in the present invention is appropriately determined in consideration of the thickness of the solid dielectric, the magnitude of the applied voltage, the purpose of using plasma, and the like, but is 0.1 to 5 mm. preferable. If the distance between the electrodes is less than 0.1 mm, it may not be sufficient to install the pair of electrodes at a distance between the electrodes, whereas if it exceeds 5 mm, it is difficult to generate uniform discharge plasma. Furthermore, the preferable distance between electrodes is 0.5-3 mm in which discharge is easy to stabilize.
[0028]
An electric field such as a high frequency, a pulse wave, or a microwave is applied between the electrodes of the counter electrode to generate plasma, but it is preferable to apply a pulse electric field, and in particular, the rise time and / or the fall time of the electric field. A pulsed electric field of 10 μs or less is preferred. If it exceeds 10 μs, the discharge state tends to shift to an arc and becomes unstable, and it becomes difficult to maintain a high-density plasma state by a pulse electric field. Also, the shorter the rise time and fall time, the more efficiently ionization of the gas during plasma generation, but it is actually difficult to realize a pulsed electric field with a rise time of less than 40 ns. A more preferable range of the rise time and the fall time is 50 ns to 5 μs. The rise time here refers to the time during which the voltage (absolute value) increases continuously, and the fall time refers to the time during which the voltage (absolute value) decreases continuously.
[0029]
The electric field strength of the pulse electric field is 1-1000 kV / cm, preferably 20-300 kV / cm. If the electric field strength is less than 1 kV / cm, the process takes too much time, and if it exceeds 1000 kV / cm, arc discharge tends to occur.
[0030]
The frequency of the pulse electric field is preferably 0.5 kHz or more. If it is less than 0.5 kHz, the plasma density is low, and the process takes too much time. The upper limit is not particularly limited, but it may be a high frequency band such as 13.56 MHz that is commonly used and 500 MHz that is used experimentally. In consideration of ease of matching with the load and handling, 500 kHz or less is preferable. By applying such a pulse electric field, the processing speed can be greatly improved.
[0031]
Moreover, it is preferable that one pulse duration in the said pulse electric field is 200 microseconds or less, More preferably, it is 3-200 microseconds. If it exceeds 200 μs, it tends to shift to arc discharge. Here, one pulse duration means a continuous ON time of one pulse in a pulse electric field composed of repetition of ON / OFF.
[0032]
In the present invention, the halogen-based gas used in the gas treatment system, and the like for example CF _4, C ₂ F _6. Further, the humidity of the atmosphere (the atmosphere around the plasma generating portion) into which the halogenated gas that has been made plasma is introduced is 20% or more at room temperature, and the upper limit is a range where no condensation occurs. A more preferable humidity range is about 40 to 60%.
[0033]
Examples of the hydrolysis treatment performed in the decomposition treatment system in the present invention include a pure water treatment method such as a treatment of spraying pure water onto a resist substrate or a treatment of immersing the resist substrate in a pure water tank. Further, the hydrolysis may be performed using a chemical solution having a hydrolysis effect instead of pure water. In this case, examples of the chemical solution include various acid aqueous solutions and various alkali aqueous solutions.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0035]
FIG. 1 is a diagram schematically showing a configuration of an embodiment of a resist stripping apparatus of the present invention.
[0036]
The resist stripping apparatus shown in FIG. 1 includes a gas processing system 100, a pure water processing system 200, a transport unit 300, and the like. In addition, as shown in FIG. 3, the resist substrate S to be processed in the present embodiment is obtained by laminating a resist S3 on a glass substrate S1 through HMDS (hydramethyldisilazane) S2. HMDS is a kind of SiO ₂ and is laminated to improve the adhesion of the resist.
[0037]
The transfer unit 300 is configured by a transfer conveyor such as a belt conveyor, for example, and sequentially transfers the resist substrate S to be processed to the plasma processing chamber 101 of the gas processing system 100 and the cleaning processing chamber 201 of the pure water processing system 200. . The plasma processing chamber 101 and the cleaning processing chamber 201 are arranged adjacent to each other.
[0038]
The plasma processing chamber 101 is provided with an atmospheric gas inlet 102 at the upper part and an exhaust outlet 103 at the lower part. An atmospheric gas supply unit 5 (FIG. 2) is connected to the atmospheric gas inlet 102, and the gas atmosphere inside the plasma processing chamber 101 is, for example, an air temperature of 20 ° C. and a humidity of 50% air (under a pressure close to atmospheric pressure). Can be maintained.
[0039]
The cleaning processing chamber 201 is provided with a clean air inlet 202 at the upper part and a drain outlet 203 at the lower part. A pure water injection device 6 is disposed inside the cleaning chamber 201. The pure water injection device 6 is disposed above the transport unit 300 (transport belt), passes through the plasma processing chamber 101, and is transferred onto the surface (resist formation surface) of the resist substrate S transported into the cleaning processing chamber 201. Irradiate with pure water.
[0040]
Next, the configuration of the gas processing system 100 will be described with reference to FIGS. 1 and 2.
[0041]
The gas processing system 100 includes a plasma generator 1, a power source 2, a gas supply unit 3, a gas supply line 4, an atmospheric gas supply unit 5, and the plasma processing chamber 101 described above.
[0042]
The plasma generating unit 1 is disposed inside the plasma processing chamber 101 at a position above the resist substrate S transferred by the transfer unit 300. The plasma generator 1 is constituted by a parallel plate type counter electrode 10 including a voltage application electrode 11 and a ground electrode 12.
[0043]
The voltage application electrode 11 and the ground electrode 12 of the counter electrode 10 are arranged to face each other so as to be parallel to each other with a predetermined distance (distance between the electrodes), and between the voltage application electrode 11 and the ground electrode 12. A plasma space 13 is formed. Each surface of the voltage application electrode 11 and the ground electrode 12 is covered with a solid dielectric (not shown).
[0044]
A gas introduction port 10 a is provided on one end (upper end) side of the plasma space 13 in the counter electrode 10, and a gas blowing port 10 b is provided on the other end (lower end) side. A gas supply unit 3 is connected to the gas introduction port 10a via a gas supply line 4. A dry halogen-based gas (for example, CF ₄ : 100%) is supplied between the voltage application electrode 11 and the ground electrode 12. Can be supplied. A glow discharge plasma is generated between the voltage application electrode 11 and the ground electrode 12 by applying an electric field (pulse electric field) from the power source 13 between the voltage application electrode 11 and the ground electrode 12 in a gas supply state. Then, the halogen-based gas is turned into plasma, and the plasma gas is blown out downward from the gas blowing port 10b.
[0045]
In the resist stripping apparatus having the above-described structure, the plasma processing chamber 101 is brought into a predetermined gas atmosphere (at a temperature of 20 ° C. and a humidity of 50%) under a pressure close to atmospheric pressure, and voltage is applied to the plasma generator 1. A halogen-based gas (CF ₄ : 100%) is supplied from the gas supply unit 3 to the plasma space 13 between the electrode 11 and the ground electrode 12 so as to be under a pressure near atmospheric pressure. An electric field (for example, a pulsed electric field) from the power source 2 is applied between the electrodes 12. By this electric field application, glow discharge plasma is generated in the plasma space 13 between the voltage application electrode 11 and the ground electrode 12, and the halogenated gas (plasma gas) converted into plasma flows outside the plasma space 13 through the gas outlet 10b. To blow out.
[0046]
Then, when the plasma gas blown out from the gas blowing port 10b is introduced into the gas atmosphere (temperature 20 ° C., humidity 50% air) in the plasma processing chamber 101, an active reaction gas is generated, and the active reaction gas is generated. Is irradiated onto the resist substrate S, the reactive gas permeates through the resist on the resist substrate S (see FIG. 3B), and etches HMDS and imparts a functional group to hydrolyze the resist. (Introduction of [—COF ₂ group]). As a result, the resist is substantially peeled from the glass substrate.
[0047]
The resist substrate S is subjected to gas processing (plasma processing) while being transported by the transport unit 300 at a predetermined scanning speed (for example, 500 mm / min or 1000 mm / min).
[0048]
The resist substrate S subjected to the above gas processing is transferred into the cleaning processing chamber 201 by the transfer unit 300 and cleaned with pure water from the pure water injection device 6. By such cleaning with pure water, the resist modified by the gas treatment is decomposed by hydrolysis. Specifically, [—COF ₂ ] is hydrolyzed (—COF ₂ + H ₂ O → COOH + HF), and the substantially stripped resist is removed by lift-off with pure water (resist stripping).
[0049]
In the above embodiment, CF ₄ is used as the halogen-based gas for plasmatization, but the same effect can be obtained by using C ₂ F ₆ instead.
[0050]
In addition, the resist modified by the plasma treatment is hydrolyzed by washing with pure water irradiation. Instead of this, the resist substrate after the plasma treatment is immersed in a pure water tank to hydrolyze the resist. You may make it perform decomposition | disassembly.
[0051]
【Example】
Examples of the present invention will be described below.
[0052]
<Example 1>
[Resist substrate]
On the glass substrate, HMDS (hydramethyldisilazane) was applied to increase the adhesion of the resist, and a 1.5 mm resist was applied on the entire surface, and then baked at 150 ° C. to prepare a resist substrate. .
[0053]
[Gas treatment equipment]
Use of gas processing system 100 shown in FIG. 2 [plasma conditions]
Halogen gas: CF ₄ (100%)
Plasma treatment atmosphere: temperature 20 ° C, humidity 50% air [power supply conditions]
Applied voltage: 10 kV
Frequency: 25 kHz (pulse electric field)
[Conveying speed]
500mm / min, 1000mm / min
With the above apparatus configuration and conditions, in the state where the halogen-based gas is converted into plasma in the plasma generation unit 1 and an active reaction gas is generated, the resist substrate S is placed at 500 mm / min and 1000 mm / min below the plasma generation unit 1. Then, the resist substrate S was irradiated with a plasma gas to perform a resist modification process. Next, the resist substrate S after the plasma treatment was immersed in pure water to perform pure water treatment (hydrolysis treatment).
[0054]
In the above processing, when the resist substrate S was transported at 500 mm / min, the resist on the glass substrate was completely peeled off. Further, when the resist substrate S before the pure water treatment was observed, wrinkles and bulges were generated in the resist, and the resist substrate S was substantially peeled off even though the resist was applied over the entire surface. It was found that the reaction gas permeated the resist and etched the HMDS under a high pressure of atmospheric pressure.
[0055]
On the other hand, when the resist substrate S is transported at 1000 mm / min, there are a part where the resist is peeled off and a part where the resist remains on the glass substrate, and the remaining resist is cracked. It was.
[0056]
In addition, no change such as white turbidity is seen on the surface of the glass substrate after the resist is peeled off under any of the conditions where the conveyance speed is 500 mm / min and 1000 mm / min, and the damage to the glass substrate is Not observed.
[0057]
Here, when the resist material after the plasma treatment and before the pure water treatment was analyzed by ESCA (Electron Spectroscopy for Chemical Analysis), introduction of [—COF ₂ group] was observed at the C bond portion. Therefore, this point (the introduction of the [-COF ₂ group]), from the viewpoint of cracking in the process of the resist is peeled off occurs, - resist weakened by hydrolysis and active halide gas [COF ₂ group] It is considered that the resist was peeled off due to the effect.
[0058]
<Example 2>
A sample was prepared by applying 0.5 μm of a resist on a silicon wafer, baking at 110 ° C., and implanting B (boron). The plasma treatment was performed on this sample while changing the atmospheric humidity (humidity of the gas atmosphere) in the range of 15 to 60%, and the resist peeling amount after the treatment was evaluated.
[0059]
As a result, the resist could be peeled off by plasma treatment for 30 seconds in a humidity range of 25% or more, but plasma treatment of 60 seconds or more was necessary in a humidity range of about 15 to 20%. From this result, it can be seen that the resist can be removed efficiently when the humidity of the atmosphere into which the halogenated gas into plasma is introduced is 20% or more.
[0060]
【The invention's effect】
As described above, according to the present invention, a process for generating an active reaction gas by introducing a halogen-based gas that has been made into plasma at a pressure close to atmospheric pressure into an atmosphere having an appropriate humidity, and its active the reaction gas by irradiating the resist substrate by etching the resist lower layer of SiO ₂ layer, and hydrolysis and treatment for imparting hydrolyze function group in the resist, a modified resist in the gas processed by the pure water or the like Since the resist on the substrate is peeled off by the process of decomposing and lifting off the resist substantially peeled off by etching with pure water or the like, the resist peeling process can be performed without damaging the substrate surface.
[0061]
In addition, since only dry halogen-based gas is converted into plasma, and the plasma-generated halogen-based gas is introduced into the atmosphere to generate an active reaction gas, it is possible to prevent deterioration of the discharge electrode for plasma generation. The cost of the discharge electrode can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of an embodiment of a resist stripping apparatus of the present invention.
FIG. 2 is a diagram schematically showing a configuration of a gas processing system used in the embodiment of FIG.
FIG. 3 is a diagram schematically showing a resist substrate to be processed in an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plasma generating part 10 Counter electrode 10a Gas inlet 10b Gas outlet 11 Voltage application electrode 12 Ground electrode 13 Plasma space 2 Power supply 3 Gas supply unit 4 Gas supply line 5 Atmospheric gas supply unit 6 Pure water injection apparatus 100 Gas processing system 101 Plasma treatment chamber 102 Atmospheric gas inlet 103 Exhaust outlet 200 Pure water treatment system (decomposition treatment system)
201 Cleaning processing chamber 202 Clean air inlet 203 Drain outlet 300 Transfer unit S Resist substrate S1 Glass substrate S2 HMDS (SiO ₂ )
S3 resist

Claims (1)

A method for removing a resist layered on a substrate via a SiO ₂ layer, which is an active reaction gas by introducing a halogen-based gas that has been converted to plasma under a pressure close to atmospheric pressure into an atmosphere having an appropriate humidity. and generating a by irradiating the active reaction gas to the substrate, and processing active reaction gas to the SiO ₂ layer is etched through the resist, and to impart hydrolyze function group to resist A resist stripping method comprising: decomposing the resist modified by the gas treatment by hydrolysis and lifting off the resist.

Images