US20050006348A1

US20050006348A1 - Method and apparatus for processing a substrate with rinsing liquid

Info

Publication number: US20050006348A1
Application number: US10/881,235
Authority: US
Inventors: Katsuhiko Miya; Akira Izumi
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 2003-07-07
Filing date: 2004-06-30
Publication date: 2005-01-13
Also published as: JP2005045206A

Abstract

A pure water supplier is connected with an inlet of the nitrogen dissolving unit. Further, there is another inlet formed in the nitrogen dissolving unit, and this inlet is connected with a nitrogen gas supply source. Nitrogen gas from the nitrogen gas supply source is dissolved in pure water supplied from the pure water supplier, thereby producing nitrogen-rich pure water. Thus nitrogen-rich rinsing liquid is produced immediately prior to rinsing. This reduces the concentration of dissolved oxygen in the rinsing liquid. This also slows down an increase of the concentration of dissolved oxygen in the rinsing liquid which has been discharged at a nozzle.

Description

CROSS REFERENCE TO RELATED APPLICATION

The disclosure of Japanese Patent Applications No.2003-192569 filed Jul. 7, 2003 and No.2004-91700 filed Mar. 26, 2003 each of which includes specification, drawings and claims is incorporated herein by reference in its entirely.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a substrate processing method and a substrate processing apparatus which require that rinsing is performed with supply of rinsing liquid to various types of substrates (hereinafter referred to simply as “substrate(s)”) such as semiconductor wafers, glass substrates for photo masks, glass substrates for liquid crystal displays, glass substrates for plasma displays and optical disk substrates.
2. Description of the Related Art
Steps of manufacturing electronic components for a semiconductor device, a liquid crystal display device or the like include a step of repeatedly executing processing such as film deposition and etching on a surface of a substrate to thereby form shrinking-patterns. It is necessary to keep the surface of the substrate clean for favorable processing, and therefore, the substrate is cleaned when needed. According to the invention described in the Japanese Patent Application Laid-Open Gazette No. H5-29292 for instance, after cleaning of a substrate surface with processing liquid which is suitable to cleaning, namely, cleaning liquid, the processing liquid remaining on the substrate surface is removed through rinsing which uses pure water as rinsing liquid. In addition, after the end of the rinsing, the substrate is rotated at a high speed, drained off of the rinsing liquid remaining on the substrate surface and dried.
However, when pure water is used as the rinsing liquid, there arises a problem that dissolved oxygen in the pure water wholly or partially oxidizes the substrate surface which has been cleaned with the cleaning liquid and an oxide film builds up on the substrate surface. Current countermeasures to solve this problem is deaeration of the pure water which is used as the rinsing liquid and consequent reduction of the concentration of dissolved oxygen in the rinsing liquid.

SUMMARY OF THE INVENTION

Nevertheless, during actual rinsing, the rinsing liquid is gushed out toward the substrate surface from a rinsing nozzle and the rinsing liquid is exposed to air as soon as it gets ejected from the nozzle. Because of this, even when the concentration of dissolved oxygen in the rinsing liquid has already been lowered through the deaeration in advance, oxygen contained in air gets dissolved in the rinsing liquid immediately after injection of the rinsing liquid from the nozzle, and the concentration of dissolved oxygen in the rinsing liquid rapidly increases. Further, oxygen within air gets dissolved in the rinsing liquid not only right after injection of the rinsing liquid from the nozzle. Rather, dissolution continuously takes place at a predetermined rate even after that. Reduction of the amount of oxygen which gets dissolved in the rinsing liquid after the rinsing liquid has been ejected at the nozzle is thus important. In other words, a very important factor for prevention of rinsing-induced oxidation of the substrate surface is reduction of the concentration of dissolved oxygen in the rinsing liquid during a period that the substrate surface remains wet with the rinsing liquid, that is, a period of time (about thirty seconds, for instance) from the start of the rinsing until the end of drying. However, effective countermeasures have not been implemented so far regarding this, leaving a large space for improvement.
A primary object of the present invention is to provide a substrate processing method and a substrate processing apparatus with which it is possible to suppress build-up of an oxide film on the substrate which would otherwise caused by dissolved oxygen contained in the rinsing liquid.
The present invention is directed to a method and an apparatus for processing a substrate. The method comprises: a wet processing step of supplying processing liquid to a substrate and subjecting the substrate to predetermined wet processing; a rinsing liquid producing step of adding nitrogen to pure water and producing rinsing liquid; and a rinsing step of supplying the rinsing liquid to the substrate after the wet processing step and rinsing the substrate with the rinsing liquid. The apparatus comprises: a rinsing liquid producer which adds nitrogen to pure water and produces nitrogen-rich rinsing liquid; and a rinsing unit, including a nozzle, which discharges the rinsing liquid supplied from the rinsing liquid producer toward the substrate, thus supplies the rinsing liquid to the substrate and rinses the substrate.
By means of such a structure, the rinsing liquid which is pure water rich with nitrogen is produced. The substrate is rinsed as this rinsing liquid is injected toward the substrate. Since a rich amount of nitrogen has been added to the pure water to produce the rinsing liquid, the concentration of dissolved oxygen in the rinsing liquid is lowered. As soon as supplied toward the substrate, the rinsing liquid gets exposed to air starts and the concentration of dissolved oxygen rises. However, added nitrogen suppresses a speed at which the concentration increases. When such rinsing liquid is used, the concentration of dissolved oxygen in the rinsing liquid would not rapidly increase during a period (about thirty seconds, for instance) from the start of injection of the rinsing liquid toward the substrate until removal of the rinsing liquid off from the substrate, thereby suppressing build-up of an oxide film on the substrate which would otherwise occur owing to dissolved oxygen in the rinsing liquid.
The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for purpose of illustration only and is not intended as a definition of the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross sectional view which shows the structure of a substrate processing apparatus as a whole according to a first embodiment of the present invention;
FIG. 2 is a block diagram which shows the structure of control executed in the substrate processing apparatus of FIG. 1;
FIG. 3 is a flow chart which shows operations of the substrate processing apparatus of FIG. 1;
FIG. 4 is a drawing which shows a relationship between the concentration of dissolved oxygen and time;
FIG. 5 is a conceptual view which shows how rinsing liquid stays from nitrogen dissolving units to nozzle outlets;
FIG. 6 is a drawing which shows the structure of a substrate processing apparatus according to a second embodiment of the present invention; and
FIG. 7 is a schematic drawing which shows the structure of a substrate processing apparatus according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

<First Embodiment>
FIG. 1 is a cross sectional view which shows the structure of a substrate processing apparatus as a whole according to a first embodiment of the present invention. FIG. 2 is a block diagram which shows the structure of control executed in the substrate processing apparatus of FIG. 1. Within this substrate processing apparatus 100, as shown in FIG. 1, a substrate W as it is held by a spin chuck 1 is subjected to film removal processing, rinsing and drying inside the same processing unit main section 101.
The spin chuck 1 comprises a disk-shaped base member 2, which also serves as a blocking member disposed on the back surface side of the substrate, and three or more holding members 3 which are formed on the top surface of the base member 2. Each one of the holding members 3 comprises a support part 3 a, which receives and supports the substrate W from below at an outer peripheral portion of the substrate W, and a restriction part 3 b which restricts the position of the outer edge of the substrate W. These holding members 3 are disposed in the vicinity of an outer peripheral portion of the base member 2. Each restriction part 3 b has such a structure that the restriction part 3 b can be in an activated state for contacting the outer edge of the substrate W and holding the substrate W and a non-activated state for moving away from the outer edge of the substrate W and releasing the substrate W. In the non-activated state, the restriction parts 3 b permits a transportation robot (not shown) load in the substrate W toward the support parts 3 a and unload the substrate W out from the support parts 3 a. After the substrate W has been put on the support parts 3 a with the surface of the substrate W directed toward above, each restriction part 3 b switches to the activated state and the spin chuck 1 holds the substrate W. This operation of the holding members 3 (the restriction parts 3 b) can be realized using a link mechanism described in the Japanese Patent Application Laid-Open Gazette No. S63-153839 for example, etc.
A top end portion of a rotation shaft 4 is attached to the bottom surface of the base member 2. A pulley 5 a is fixed to a bottom end portion of the rotation shaft 4. Rotation force of a motor 5 is thus transmitted to the rotation shaft 4 via a belt 5 c which stretches around this pulley 5 a and another pulley 5 b which is fixed to a rotation shaft of the motor 5. Therefore, as the motor 5 rotates, the substrate W held by the spin chuck 1 rotates about the center of the substrate W.
There is a nozzle 6 disposed to a central portion of the base member 2. The nozzle 6 is connected with a liquid supplier 50 which supplies processing liquid, rinsing liquid or the like to the back surface of the substrate through a pipe 7 which is internally connected along the central axis of a hollow rotation shaft 4 and through a pipe 8. The structure and operations of the liquid supplier 50 will be described in detail later.
There is an opening 16 formed in the central portion of the base member 2 in such a manner that the opening 16 is coaxial with the nozzle 6. The opening 16 is communicated with a gas supplier 20 through a hollow section 17 and a pipe 19. The hollow section 17 is disposed coaxially with the pipe 7 inside the rotation shaft 4. In the pipe 19 a shut-off valve 18 is interposed. Hence, when the shut-off valve 18 is open, inert gas (such as nitrogen gas) is supplied between the base member 2 which functions as “atmosphere blocker” of the present invention and the back surface of the substrate W so that the space between the base member 2 and the back surface of the substrate W can therefore be purged into an inert gas atmosphere.
A blocking member 21 which functions as the “atmosphere blocker” of the present invention is disposed above the spin chuck 1. The blocking member 21 is attached to a bottom end portion of a suspension arm 22 which is disposed along the vertical direction. In addition, a motor 23 is disposed to a top end portion of the suspension arm 22 so that when the motor 23 is driven, the blocking member 21 rotates about the suspension arm 22. The rotation shaft core of the rotation shaft 4 of the spin chuck 1 coincides with the rotation shaft core of the suspension arm 22, allowing that the base member 2 serving as the atmosphere blocker, the blocking member 21 and the substrate W which is held by the spin chuck 1 coaxially rotate. Further, the motor 23 rotates the blocking member 21 in the same direction at about the same rotation speed as (the substrate W which is held by) the spin chuck 1.
There is a nozzle 25 in the central portion of the blocking member 21. The nozzle 25 is connected with a liquid supplier 70 which supplies processing liquid, rinsing liquid or the like to the surface of the substrate through a pipe 26 which is internally connected along the central axis of the hollow suspension arm 22 and through a pipe 27. The structure and operations of the liquid supplier 70 will be described in detail later.
There is an opening 35 formed in the central portion of the blocking member 21 in such a manner that the opening 35 is coaxial with the nozzle 25. The opening 35 is communicated with a gas supplier 39 through a hollow section 36 and a pipe 38. The hollow section 36 is disposed coaxially with the pipe 26 inside the suspension arm 22. In the pipe 38 a shut-off valve 37 is interposed. As the shut-off valve 37 is opened with the blocking member 21 positioned in the vicinity of the surface of the substrate W which is held by the spin chuck 1, inert gas (such as nitrogen gas) is supplied between the blocking member 21 and the surface of the substrate W and the space between the blocking member 21 so that the surface of the substrate W can therefore be purged into an inert gas atmosphere. In this embodiment, the hollow sections 17 and 36, the shut-off valves 18 and 37, the pipes 19 and 38 and the gas suppliers 20 and 39 thus constitute “inert gas supplier.”
The structures of the liquid suppliers 50 and 70 will now be described. Since the liquid suppliers 50 and 70 have the identical structures, the structure of the liquid supplier 50 alone will be described. The structure of the other liquid supplier 70 will be denoted at corresponding reference symbols but will not be described. The liquid supplier 50 is disposed inside the processing unit main section 101 and comprises a hydrofluoric acid supply source 51 which supplies hydrofluoric acid and a nitrogen dissolving unit 58. The hydrofluoric acid supply source 51 is connected with a mixing unit 55 through a pipe 54 in which a shut-off valve 53 is interposed, while the a pure water supplier 200 which is disposed separately from the processing unit main section 101 is connected with an inlet of the nitrogen dissolving unit 58 through a pipe 201. Further, there is another inlet formed in the nitrogen dissolving unit 58, and this inlet is connected with a nitrogen gas supply source not shown. Nitrogen gas from the nitrogen gas supply source is dissolved in pure water supplied from the pure water supplier 200, thereby producing nitrogen-rich pure water. In addition, the nitrogen dissolving unit 58 is connected with the mixing unit 55 through a pipe 57 in which a shut-off valve 56 is interposed. As the shut-off valves 53 and 56 are opened and closed in accordance with a control command fed from a controller 80 which controls the entire apparatus, hydrofluoric solution or pure water in which nitrogen has been dissolved is fed to the pipe 8 from the mixing unit 55 and the hydrofluoric solution or the pure water is selectively supplied toward the surface of the substrate W. In other words, when the shut-off valves 53 and 56 are all opened, hydrofluoric acid and pure water are supplied to the mixing unit 55 and the hydrofluoric solution having a predetermined concentration is prepared. The hydrofluoric solution is gushed out at the nozzle 6 through the pipe 8 toward the back surface of the substrate W, and a film consequently adhering to the back surface of the substrate is removed through etching. When only the shut-off valve 56 is opened, rinsing can be performed with the rinsing liquid, namely, the pure water in which nitrogen has been dissolved supplied at the nozzle 6 through the pipe 8 toward the back surface of the substrate W. As viewed from the back surface of the substrate W, the pipes 7 and 8 and the nozzle 6 thus function as “rinsing unit” of the present invention, while the nitrogen dissolving unit 58 functions as “rinsing liquid producer” of the present invention. As the nitrogen dissolving unit 58, a bubbling apparatus which uses a tank or a conventional apparatus which uses a hollow yarn is used. As viewed from the front surface of the substrate W, the pipes 26 and 27 and the nozzle 25 thus function as the “rinsing unit” of the present invention, while an oxygen dissolving unit 78 functions as the “rinsing liquid producer” of the present invention.
Further, a cup 40 which prevents the processing liquid from splashing around is disposed around the spin chuck 1. The processing liquid collected by the cup 4 is discharged outside the apparatus, and although not shown, stored in a tank which is disposed below the cup 40.
Operations of the substrate processing apparatus which has the structure above will now be described with reference to FIG. 3. FIG. 3 is a flow chart which shows the operations of the substrate processing apparatus of FIG. 1. In this substrate processing apparatus 100, the transportation robot transports an unprocessed substrate W to the spin chuck 1, and after the holding members 3 have held the substrate W (Step S1), film removal processing, rinsing and drying are executed in this order with the respective portions of the apparatus controlled as described below by the controller 80 which controls the entire apparatus.
At Step S2, after positioning the blocking member 21 close to the surface of the substrate W which is held by the spin chuck 1, with the substrate W held between the base member 2 and the blocking member 21, the motor 5 is driven and starts and the substrate W is rotated together with the spin chuck 1. Further, with the shut-off valves 53, 73, 56 and 76 all opened, hydrofluoric acid and pure water are supplied to the mixing units 55 and 75, thereby preparing the hydrofluoric solution having a predetermined concentration and pressure-feeding the hydrofluoric solution to the nozzles 6 and 25. Supply of the hydrofluoric solution to the both surfaces of the substrate W at the nozzles 6 and 25 is thus initiated (Step S3). This starts removal of a film adhering to the both surfaces of the substrate W through etching.
Upon confirmation at Step S4 of completion of the film removal processing, the shut-off valves 53, 73, 56 and 76 are all closed, and after stopping the supply of the hydrofluoric solution toward the substrate W at the nozzles 6 and 25, the substrate W is rotated at a high speed and the hydrofluoric solution is spin-removed and discharged outside the apparatus.
As draining of the hydrofluoric solution thus ends (Step S5), the shut-off valves 18 and 37 are opened and inert gas is supplied to the space between the base member 2 and the blocking member 21. After changing an atmosphere surrounding the substrate W to an inert gas atmosphere, the shut-off valves 56 and 76 are opened only for a certain period of time, the nitrogen-rich pure water is supplied as the rinsing liquid to the both major surfaces of the substrate W and the substrate W is rinsed (Step S6). After the end of the rinsing with the shut-off valves 56 and 76 close, the substrate W is kept rotating until the substrate W has dried. Upon drying of the substrate W, the rotating of the substrate W is stopped, the shut-off valves 18 and 37 are closed and the supply of the inert gas is stopped (Step S7).
As the series of substrate processing (the film removal processing, the rinsing and the drying) finishes in this manner, the blocking member 21 is moved away from the surface of the substrate W which is held by the spin chuck 1, and after the holding members 3 have released the substrate, the transportation robot transports thus processed substrate W to the next substrate processing apparatus (Step S8).
As described above, the preferred embodiment requires that nitrogen is dissolved in pure water and the nitrogen-rich rinsing liquid is accordingly produced immediately before the rinsing, and therefore, the preferred embodiment attains the following effects. First, it is possible to reduce the concentration of dissolved oxygen in the rinsing liquid. In addition, during the period (e.g., about thirty seconds) from discharge of the rinsing liquid toward the substrate W at the nozzles 6 and 25 until the completion of the drying (i.e., until the rinsing liquid has been removed from the substrate W), it is possible to effectively suppress a rapid hike of the concentration of dissolved oxygen in the rinsing liquid. These effects realize a low dissolved oxygen concentration in the rinsing liquid during the rinsing and the drying, thereby suppressing build-up of an oxide film on the substrate owing to dissolved oxygen in the rinsing liquid. The latter one of these effects, namely, the slowed increase of the concentration of dissolved oxygen is based on the new finding which the inventor of the present invention has obtained for the first time through various types of experiments and the like. Therefore, this will now be described in detail with reference to FIG. 4.
FIG. 4 shows how the concentration of dissolved oxygen increases with time in two types of pure water, one in which a very small amount of nitrogen has been dissolved (hereinafter referred to as “low nitrogen concentration water”)and the other in which nitrogen has been richly dissolved (hereinafter referred to as “high nitrogen concentration water”). The curves appearing in FIG. 4 were measured in the following manner. First, two containers respectively filled up with the low nitrogen concentration water and the high nitrogen concentration water were prepared. For every certain time, the liquid was taken from each container and the concentration of dissolved oxygen in each liquid was measured using DKK-TOA CORPORATION's DO-32A. The symbol t₀denotes the time at which the rinsing liquid is discharged out at the nozzles 6 and 25 (immediately after the two containers have been respectively filled up with the low nitrogen concentration water and the high nitrogen concentration water), the symbol t₁denotes the time at which the discharge of the rinsing liquid toward the substrate W at the nozzles 6 and 25 ends and the symbol t2 denotes the time at which the drying completes (i.e., the time at which the rinsing liquid has been removed off from the substrate W).
While it is desirable that the concentration of dissolved oxygen in the rinsing liquid is measured while the substrate processing apparatus is actually executing the rinsing and the drying, it is still technically impossible to measure the concentration of dissolved oxygen in the rinsing liquid on the substrate W while the processing is ongoing. For this reason, from the concentration values of dissolved oxygen in the low and the high nitrogen concentration water thus measured using the above means, the concentration values of dissolved oxygen in the rinsing liquid on the substrate W during the rinsing and the drying were estimated.
The different concentrations of dissolved nitrogen in the rinsing liquid give rise to no major difference between the concentration values of dissolved oxygen in the rinsing liquid at the time (t₀) that the rinsing liquid is injected out at the nozzles 6 and 25. However, at the time (t₁) that the injection of the rinsing liquid toward the substrate W ends, there already is a difference between the concentration values of dissolved oxygen in the rinsing liquid. This leads to the following conclusion: When nitrogen has been richly dissolved in the rinsing liquid in advance, the concentration of dissolved oxygen in the rinsing liquid is suppressed from increasing right after the injection toward the substrate at the nozzles. It is therefore possible to suppress build-up of an oxide film on the substrate W owing to dissolved oxygen in the rinsing liquid at the initial stage of the rinsing.
Meanwhile, the rinsing liquid remains on the substrate W during the rinsing of course, and additionally, until the subsequent drying has finished. Hence, it is necessary to consider the concentration of dissolved oxygen in the rinsing liquid during the period until the end of the drying. During this period as well, there is a big difference between the concentration values of dissolved oxygen in the rinsing liquid as shown in FIG. 4. One can therefore conclude as follows: When nitrogen has been richly dissolved in the rinsing liquid in advance, the speed at which the concentration of dissolved oxygen in the rinsing liquid increases is suppressed during the rinsing and the drying. This permits execution of the rinsing and the drying while maintaining a low level of dissolved oxygen in the rinsing liquid which is present on the substrate W and accordingly suppresses build-up of an oxide film on the substrate W.
Further, since the atmosphere surrounding the substrate W is turned to the inert gas atmosphere during execution of the rinsing and the drying, it is possible to reduce the amount of oxygen around the substrate which could be dissolved in the rinsing liquid. Hence, it is possible to further suppress an increase of the concentration of dissolved oxygen in the rinsing liquid during the period (e.g., about thirty seconds) from discharge of the rinsing liquid toward the substrate W at the nozzles until removal of the rinsing liquid off from the substrate W. As a result, build-up of an oxide film on the substrate W is more effectively suppressed.
In addition, according to this preferred embodiment, the nitrogen dissolving units 58 and 78 are disposed inside the processing unit main section 101, thereby shortening the paths which the rinsing liquid follows after produced by richly dissolving nitrogen in pure water before until discharged out at the nozzles 6 and 25. For this reason, the rinsing liquid is supplied to the substrate W as soon as the rinsing liquid has been produced, which further effectively suppresses an increase of the concentration of dissolved oxygen in the rinsing liquid.
With respect to the locations of the nitrogen dissolving units 58 and 78, the nitrogen dissolving units 58 and 78 are preferably disposed such that one liter of the rinsing liquid or less will remain in the rinsing liquid paths from the nitrogen dissolving units 58 and 78 to the outlets of the nozzles 6 and 25. This is for the following reason: Since rinsing usually demands approximately one through four liters of the rinsing liquid per substrate, when the nitrogen dissolving units 58 and 78 are disposed as described above such that the capacity in each path will be less than the amount of the rinsing liquid demanded per substrate, the rinsing liquid produced in the nitrogen dissolving units 58 and 78 will be all used for rinsing of one substrate W. Hence, where a plurality of substrates W are to be processed successively, the rinsing liquid which was used during the previous rinsing would have exited from the paths by the time that rinsing of the next substrate W starts. In consequence, it is possible to make the maximum use of the effect which is realized by adding nitrogen that dissolution of oxygen in the rinsing liquid is suppressed, and hence, effectively suppress an increase of the concentration of dissolved oxygen in the rinsing liquid.
As ranges for suppressing an increase of the concentration of dissolved oxygen in the rinsing liquid, the nitrogen dissolving units 58 and 78 are preferably disposed such that 200 liters or less of the rinsing liquid will remain in the rinsing liquid paths from the nitrogen dissolving units 58 and 78 to the outlets of the nozzles 6 and 25. The ranges are determined by such an upper limit amount of the rinsing liquid which ensures that while nitrogen added to the produced rinsing liquid stays effective, the rinsing liquid can be all fed to the substrate W to rinse the substrate W and removed off from the substrate W. The upper limit amount of the rinsing liquid will now be described in detail with reference to FIG. 5.
FIG. 5 is a conceptual diagram which shows how the rinsing liquid remains from the oxygen dissolving units to the outlets of the nozzles. The respective bars in the graph represent the states of the rinsing liquid in the rinsing liquid paths from the nitrogen dissolving units 58 and 78 (the right-hand end) to the outlets of the nozzles 6 and 25 (the left-hand end). The time instances T₀, T₁, T₂. . . appearing vertically denote the time at which processing of each substrate W starts when a plurality of substrates W are to be processed successively (during processing of the single wafer type). Assuming that the amount U of the rinsing liquid is used per substrate W, during rinsing of the first substrate, out of the rinsing liquid L (T₀) produced at the time T₀, the rinsing liquid U is discharged at the nozzles 6 and 25 (the left-hand end). As a result, at the time T₁that processing of the second substrate starts, the rinsing liquid paths are replenished with the rinsing liquid L (T₁) newly produced in the nitrogen dissolving units 58 and 78 (the right-hand end). In a similar fashion, at the time T₂that processing of the third substrate starts, out of the rinsing liquid L (T₁), the rinsing liquid U is discharged at the nozzles 6 and 25 (the left-hand end) and the rinsing liquid paths are replenished with the rinsing liquid L (T₂) which has been newly produced in the nitrogen dissolving units 58 and 78 (the right-hand end).
Thus, when the capacity of the rinsing liquid remaining in the rinsing liquid paths from the nitrogen dissolving units 58 and 78 to the outlets of the nozzles 6 and 25 is beyond the amount U of the rinsing liquid used per substrate, even at the time instants T₁, T₂. . . , the rinsing liquid L (T₀) produced at the time T₀stays in the rinsing liquid paths. When the rinsing liquid thus stays longer, the effect which is realized by adding nitrogen becomes weaker as time goes by and oxygen gets dissolved in the rinsing liquid. This leads to an increase of the concentration of dissolved oxygen in the rinsing liquid which has been injected out at the nozzles 6 and 25. Noting this, even when the rinsing liquid remains long in the rinsing liquid paths, it is necessary to execute rinsing and remove the rinsing liquid off from each substrate W while the effect of added nitrogen is still continuing.
When the period during which the effect of added nitrogen remains valid is TN (where N is a natural number) for instance, if the rinsing liquid L (T₀) produced at the time T₀is still present in the rinsing liquid paths during processing of the N-th substrate, as the rinsing liquid is ejected at the nozzles 6 and 25, the concentration of dissolved oxygen in the rinsing liquid increases since the effect of added nitrogen has got weaker. Hence, it is needed to restrict the capacity in the rinsing liquid paths such that the rinsing liquid L (T₀) produced at the time T₀will not remain at the time TN.
Therefore, the inventor of the present invention comprehensively studied processing time required per substrate (i.e., a time interval between execution of rinsing of the previous substrate W and execution of rinsing of the next substrate W), the amount of the rinsing liquid used per substrate and duration of the effect of added nitrogen, based on various types of experiment data and the like. As a result, the inventor of the present invention clarified that when the capacity of the rinsing liquid remaining in the rinsing liquid paths from the rinsing liquid producer to the outlets of the nozzles was 200 liters or less, while nitrogen added to the produced rinsing liquid stayed effective, the rinsing liquid would be all fed to a substrate W (a plurality of substrates W) to rinse the substrate W and removed off from the substrate W (the plurality of substrates W).
<Second Embodiment>
FIG. 6 is a drawing which shows the structure of a substrate processing apparatus according to a second embodiment of the present invention. A major difference of the second embodiment from the first embodiment is that the apparatus of the second embodiment comprises deaeration units. To be more specific, pure water supplied from utilities in a plant where the substrate processing apparatus 100 is installed is fed directly to the nitrogen dissolving units 58 and 78 to produce the rinsing liquid according to the first embodiment. On the other hand, the second embodiment requires that immediately after deaeration of pure water in the deaeration units 59 and 79, the pure water is supplied to the nitrogen dissolving units 58 and 78 to produce the rinsing liquid. In the second embodiment, the deaeration units 59 and 79 are additionally disposed within the processing unit main section 101. Hence, the following effects are further attained.
In the case of a plant where the substrate processing apparatus 100 is installed, pure water is deaerated in a deaeration facility next to the plant and the concentration of dissolved oxygen in pure water is reduced. Thus deaerated pure water is supplied to a utility line (pipe 201). However, by the time that this pure water arrives at the substrate processing apparatus 100 via the utility line from the deaeration facility, oxygen would have got dissolved in the pure water and the concentration of dissolved oxygen in the pure water would have started increasing right after the deaeration. In contrast, the deaeration units 59 and 79 are disposed adjacent to the nitrogen dissolving units 58 and 78 in the second embodiment. Owing to this, the pure water in which the concentration of dissolved oxygen has dropped low by means of the deaeration performed in the deaeration units 59 and 79 is immediately supplied to the nitrogen dissolving units 58 and 78, and therefore, the rinsing liquid having a lower concentration of dissolved oxygen than in the first embodiment is produced.
In the substrate processing apparatus 100 as well which has such a structure, the series of substrate processing (the film removal processing, the rinsing and the drying) is executed in accordance with the operation sequence shown in FIG. 3, thereby achieving similar effects to those according to the first embodiment. In other words, it is possible to further suppress an increase of the concentration of dissolved oxygen in the rinsing liquid during the period (e.g., about thirty seconds) from discharge of the rinsing liquid toward the substrate W at the nozzles 6 and 25 until the completion of the drying (i.e., until the rinsing liquid has been removed from the substrate W). As a result, build-up of an oxide film on the substrate W is suppressed more as compared to where conventional methods are used. Further, since the rinsing liquid having a lower concentration of dissolved oxygen than in the previous preferred embodiment is produced according to the second embodiment, build-up of an oxide film on the substrate W is more effectively suppressed.
According to the second embodiment as well, since the deaeration units 59 and 79 are disposed together with the nitrogen dissolving units 58 and 78 within the processing unit main section 101, nitrogen is added after the deaeration of the pure water and the rinsing liquid is consequently produced, whereby the paths for the rinsing liquid until discharge at the nozzles 6 and 25 are shortened. Thus produced rinsing liquid is supplied to the substrate W quickly, and an increase of the concentration of dissolved oxygen in the rinsing liquid is more effectively suppressed.
With respect to the locations of the deaeration units 59 and 79, for a similar reason to that regarding the nitrogen dissolving units 58 and 78 in the first embodiment, it is desirable that the capacity of the rinsing liquid remaining in the rinsing liquid paths from the deaeration units 59 and 79 respectively to the outlets of the nozzles 6 and 25 is one liter or less. As ranges for suppressing an increase of the concentration of dissolved oxygen in the rinsing liquid, the deaeration units 59 and 79 are preferably disposed such that the capacity of the rinsing liquid remaining in the rinsing liquid paths from the deaeration units 59 and 79 respectively to the outlets of the nozzles 6 and 25 will be 200 liters or less.
<Third Embodiment>
FIG. 7 is a schematic drawing which shows the structure of a substrate processing apparatus according to a third embodiment of the present invention. A major difference of the third embodiment from the first embodiment is of the unit arrangement. While the nitrogen dissolving unit 58 (78) is disposed within the processing unit main section 101 according to the first embodiment, the third embodiment requires that the nitrogen dissolving unit 58 (78) is disposed outside the processing unit main section 101. To be more specific, the nitrogen dissolving unit 58 (78) is interposed in the utility line (pipe 201) of a plant which links pure water supplier 200 to the processing unit main section 101. To thus dispose the nitrogen dissolving unit 58 (78) outside the processing unit main section 101 attains an advantage that the processing unit main section 101 is fabricated in a compact size. Within such an apparatus in which the nitrogen dissolving unit 58 (78) is disposed outside the processing unit main section 101, the location of the nitrogen dissolving unit 58 (78) may be freely determined.
The pure water supplier 200 will now be described in detail with reference to FIG. 7. The pure water supplier 200 comprises a pure water supply source 200 a for supplying pure water and a circulation path 200 b for returning pure water which has come from the pure water supply source 200 a back to the pure water supply source 200 a and accordingly circulating the pure water. The pure water circulating in the circulation path 200 b is deaerated in a deaeration facility (not shown) and the concentration of dissolved oxygen in the pure water consequently decreases. However, even when the concentration of dissolved oxygen in the pure water has been reduced during the deaeration, oxygen gets dissolved in the pure water while the pure water reaches the processing unit main section 101 via the utility line (pipe 201) branching off from the circulation path 200 b and leading to the processing unit main section 101. The concentration of dissolved oxygen in pure water consequently increases.
In contrast, the nitrogen dissolving unit 58 (78) is disposed outside the processing unit main section 101 according to the third embodiment. Hence, the nitrogen dissolving unit 58 (78) adds an abundant amount of nitrogen to the pure water, and an increase of the concentration of dissolved oxygen in the pure water arriving at the processing unit main section 101 is suppressed. While it is desirable that the nitrogen dissolving unit 58 (78) is disposed right behind the branching from the circulation path 200 b where oxygen could be dissolved in the pure water in this regard, considering the duration of the effect of added nitrogen, it is equally desirable that the nitrogen dissolving unit 58 (78) is disposed such that the capacity of the rinsing liquid remaining in the rinsing liquid path from the nitrogen dissolving unit 58 (78) to the outlet of the nozzle 6 (25) will be 200 liters or less.
According to the third embodiment as well, as in the second embodiment, the deaeration unit 59 (79) may be additionally disposed and the pure water as it is immediately after deaerated in the deaeration unit 59 (79) may be supplied to the nitrogen dissolving unit 58 (78) to produce the rinsing liquid. As ranges for suppressing an increase of the concentration of dissolved oxygen in the rinsing liquid, the deaeration unit 59 (79) is preferably disposed such that the capacity of the rinsing liquid remaining in the rinsing liquid paths from the deaeration unit 59 (79) to the outlets of the nozzle 6 (25) will be 200 liters or less.
The present invention is not limited to the preferred embodiments above, but may be modified in various manners in addition to the preferred embodiments above, to the extent not deviating from the object of the invention. For instance, although the embodiments described above require that the both surfaces of a substrate W are processed through the series of processing, the present invention is applicable to a substrate processing apparatus in which only one surface is subjected to substrate processing.
Further, hydrofluoric solution is supplied to a substrate W as the processing liquid and the substrate is wet-processed in the preferred embodiments above. The present invention may be applied to a substrate processing apparatus in which other processing liquid than this (such as cleaning liquid or developing liquid) is supplied to a substrate and the substrate is processed through predetermined wet processing (such as washing and development). In essence, the present invention is applicable generally to such substrate processing apparatuses in which rinsing liquid is supplied to substrates and the substrates are rinsed.
Further, while the rinsing liquid as it has been produced is supplied to a substrate W for rinsing in the preferred embodiments above, the rinsing may be performed using such rinsing liquid which has been mixed with hydrofluoric acid and accordingly has a PH value of 6 or smaller. Use of such rinsing liquid effectively prevents oxidation (creation of a water mark). In this case, the shut-off valve 56 is opened and the shut-off valve 53 is adjusted during rinsing, whereby a predetermined amount of hydrofluoric acid is added to the rinsing liquid. The rinsing liquid is thus controlled to a predetermined PH value. The PH value may be controlled not necessarily after producing the rinsing liquid but also before addition of nitrogen to pure water. In addition, acid used for control of the PH value of the rinsing liquid is not limited to hydrofluoric acid. Hydrochloric acid may be used instead, for instance.
Still further, although nitrogen is dissolved in pure water to produce the nitrogen-rich rinsing liquid in the preferred embodiments above, it is more preferable that the rinsing liquid is produced using ultrapure water instead of using pure water.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as other embodiments of the present invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.

Claims

1. A substrate processing method, comprising:

a wet processing step of supplying processing liquid to a substrate and subjecting said substrate to predetermined wet processing;

a rinsing liquid producing step of adding nitrogen to pure water and producing rinsing liquid; and

a rinsing step of supplying said rinsing liquid to said substrate after said wet processing step and rinsing said substrate with said rinsing liquid.

2. The substrate processing method of claim 1, further comprising a deaeration step of deaerating said pure water immediately before said rinsing liquid producing step.

3. The substrate processing method of claim 1, wherein said rinsing step is performed in an inert gas atmosphere.

4. A substrate processing apparatus in which rinsing liquid is supplied to a substrate and rinses said substrate, said apparatus comprising:

a rinsing liquid producer which adds nitrogen to pure water and produces nitrogen-rich rinsing liquid; and

a rinsing unit, including a nozzle, which discharges said rinsing liquid supplied from said rinsing liquid producer toward said substrate, thus supplies said rinsing liquid to said substrate and rinses said substrate.

5. The substrate processing apparatus of claim 4, further comprising a processing unit main section, wherein

said rinsing liquid producer and said rinsing unit are disposed within said processing unit main section.

6. The substrate processing apparatus of claim of 5, further comprising a deaerator which deaerates pure water within said processing unit main section, wherein

said rinsing liquid producer adds nitrogen to said pure water which has been deaerated by said deaerator and produces said rinsing liquid.

7. The substrate processing apparatus of claim of 5, further comprising a deaerator which deaerates said pure water outside said processing unit main section, wherein

8. The substrate processing apparatus of claim 4, further comprising a processing unit main section, wherein

said rinsing unit is disposed within said processing unit main section while said rinsing liquid producer is disposed outside said processing unit main section.

9. The substrate processing apparatus of claim of 8, further comprising a deaerator which deaerates said pure water outside said processing unit main section, wherein

10. The substrate processing apparatus of claim 4, wherein said rinsing liquid producer is disposed such that the capacity of said rinsing liquid remaining in a rinsing liquid path from said rinsing liquid producer to an outlet of said nozzle will be 200 liters or less.

11. The substrate processing apparatus of claim of 4, further comprising a deaerator which deaerates said pure water, wherein

said rinsing liquid producer adds nitrogen to said pure water which has been deaerated by said deaerator and produces said rinsing liquid, and

said deaerator is disposed such that the capacity of said rinsing liquid remaining in a rinsing liquid path from said deaerator to an outlet of said nozzle will be 200 liters or less.

12. The substrate processing apparatus of claim of 4, further comprising atmosphere blocker which is disposed with a distance from said substrate while facing said substrate to which said rinsing liquid is supplied; and

inert gas supplier which supplies inert gas into a space which is created between said atmosphere blocker and said substrate.