Substrate processing method and substrate processing system

A substrate processing method capable of preventing a reduction in productivity of the fabrication of a semiconductor device from a substrate. An HF gas is supplied toward a wafer having a thermally-oxidized film, a BPSG film, and a deposit film, to thereby selectively etch the BPSG film and the deposit film using fluorinated acid. A residual matter of H2SiF6 produced at the time of etching is decomposed into HF and SiF4 by being heated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate processing method and a substrate processing system, and more particularly, to a substrate processing method for removing a hard mask and a deposit film from a substrate, and a substrate processing system for implementing the substrate processing method.

2. Description of the Related Art

A semiconductor wafer W as shown inFIG. 7has been known, which has a single-crystal silicon substrate base71on which a thermally-oxidized film72made of SiO2, films73,74, and an oxide film such as a BPSG (boron phosphorous silicate glass) film75are formed in layers. To form a hole or a trench (groove) in the single-crystal silicon substrate base71of the wafer W, the silicon substrate base71is dry-etched in a depressurized environment using a plasma generated from a halogen-based processing gas such as an HBr (hydrogen bromide) gas and using the BPSG film75as a hard mask. At that time, the plasma reacts with silicon (Si) and as a result, a deposit film76of SiOBr is formed on a surface of the hole or the like. The deposit film76functions to suppress the single-crystal silicon substrate base71from being dry-etched.

The BPSG film75and the deposit film76of the wafer W can cause a conduction failure of a semiconductor device fabricated from the wafer W, and therefore these films must be removed. To remove the hard mask such as the BPSG film75, a wet etching is employed (see for example, Japanese Laid-open Patent Publication No. 2005-150597).

Since a wet etching uses a chemical solution, a wet etching apparatus cannot be installed on the same substrate processing system together with a dry etching apparatus for dry-etching wafers W in a depressurized environment. In other words, the wet etching apparatus must be installed at a location different from the dry etching apparatus. Furthermore, the wafer W having been formed with a hole or the like in its single-crystal silicon substrate base71using the dry etching apparatus must be transferred out from the dry etching apparatus and then transferred in the ambient air before it is transferred into the wet etching apparatus. As a result, the substrate processing process is made complicated.

Moreover, the deposit film76made of SiOBr of the wafer W can react with the moisture content of the ambient air during the transfer of the wafer W in ambient air. Thus, it is necessary to manage a time period (Q-Time) during which the wafer W is exposed. More specifically, the exposure time period must be shortened to a minimum. The management of the exposure time period requires considerable man-hours.

In other words, the removal of the BPSG film75and the deposit film76causes a reduction in productivity of the fabrication of semiconductor devices from wafers W.

SUMMARY OF THE INVENTION

The present invention provides a substrate processing method and a substrate processing system capable of preventing a reduction in productivity of the fabrication of a semiconductor device from a substrate.

According to a first aspect of the present invention, there is provided a substrate processing method for processing a substrate having a single-crystal silicon substrate base, a first oxide film formed by a thermal oxidation treatment, and a second oxide film containing an impurity, a part of the single-crystal silicon substrate base being exposed through the first and second oxide films, comprising a plasma etching step of etching the exposed single-crystal silicon substrate base using a plasma of a halogen-based gas, an HF gas supply step of supplying an HF gas toward the substrate, and a substrate heating step of heating the substrate to which the HF gas is supplied.

With the substrate processing method according to the present invention, the single-crystal silicon substrate base partly exposed through the first oxide film formed by a thermal oxidation treatment and the second oxide film containing an impurity is etched by the plasma of the halogen-based gas, the HF gas is supplied to the substrate, and the substrate is heated. When the single-crystal silicon substrate base is etched by the plasma of the halogen-based gas, a deposit film is formed. From the HF gas, fluorinated acid is generated that selectively etches the deposit film and the second oxide film and produces a residual matter that can be decomposed by being heated. Thus, the deposit film and the second oxide film can be removed in a dry environment, and therefore, an apparatus for etching the single-crystal silicon substrate base and an apparatus for removing the deposit film and the second oxide film can be installed together on the same substrate processing system. As a result, the deposit film and the second oxide film of the substrate whose single-crystal silicon substrate base has been etched can be removed, without the substrate being exposed to the ambient air, whereby the substrate processing processes can be simplified and the necessity of managing a time period of exposure of the substrate to the ambient air can be eliminated, making it possible to prevent a reduction in productivity of the fabrication of a semiconductor device from the substrate.

In the present invention, it is possible to make the substrate so as not to be exposed to the ambient air during the plasma etching step, the HF gas supply step, and the substrate heating step.

In that case, the substrate is not exposed to the ambient air while the substrate is being etched by the plasma of the halogen-based gas, and the HF gas is supplied toward the substrate which is then heated. This ensures that it is unnecessary to manage the time period of exposure of the substrate to the ambient air.

The substrate can be heated in an N2gas ambient in the substrate heating step.

In that case, the substrate is heated in the N2gas ambient. The N2gas forms a stream of gas that catches and transfers the residual matter decomposed by being heated. Thus, the deposit film and the second oxide film can reliably be removed.

According to a second aspect of the present invention, there is provided a substrate processing method for processing a substrate having a single-crystal silicon substrate base, a first oxide film formed by a thermal oxidation treatment, and a second oxide film containing an impurity, a part of the single-crystal silicon substrate base being exposed through the first and second oxide films, comprising a plasma etching step of etching the exposed single-crystal silicon substrate base using a plasma of a halogen-based gas, an HF gas supply step of supplying an HF gas toward the substrate, and a cleaning gas supply step of supplying a cleaning gas containing at least NH3gas toward the substrate to which the HF gas is supplied.

With this substrate processing method, the single-crystal silicon substrate base of the substrate partly exposed through the first oxide film formed by the a thermal oxidation treatment and the second oxide film including impurity is etched by the plasma of the halogen-based gas, the HF gas is supplied to the substrate, and the cleaning gas containing at least NH3is further supplied to the substrate. When the single-crystal silicon substrate base is etched by the plasma of the halogen-based gas, a deposit film is formed. Fluorinated acid produced from the HF gas selectively etches the deposit film and the second oxide film, and produces a residual matter. The NH3gas reacts with the residual matter to produce a product of reaction that can easily be sublimated. Since the reaction product is easily sublimated, it is possible to remove the deposit film and the second oxide film in a dry environment, and therefore, an apparatus for etching the single-crystal silicon substrate base and an apparatus for removing the deposit film and the second oxide film can be installed together on the same substrate processing system. After the single-crystal silicon substrate base of the substrate is etched, the deposit film and the second oxide film can be removed without exposing the substrate to the ambient air. Thus, the substrate processing process can be simplified and the need of managing a time period of exposure of the substrate to the ambient air can be eliminated, making it possible to prevent a reduction in the productivity of the fabrication of a semiconductor device from the substrate.

The substrate processing method can permit the substrate not to be exposed to the ambient air during the plasma etching step, the HF gas supply step, and the cleaning gas supply step.

In that case, while the substrate is being etched by the plasma of the halogen-based gas and the HF gas and the cleaning gas are being supplied toward the substrate, the substrate is not exposed to the ambient air, making it unnecessary to manage the time period of exposure of the substrate to the ambient air.

According to a third embodiment of the present invention, there is provided a substrate processing system for processing a substrate having a single-crystal silicon substrate base, a first oxide film formed by a thermal oxidation treatment, and a second oxide film containing an impurity, a part of the single-crystal silicon substrate base being exposed through the first and second oxide films, comprising a plasma etching apparatus adapted to etch the exposed single-crystal silicon substrate base using a plasma of a halogen-based gas, an HF gas supply apparatus adapted to supply an HF gas toward the substrate, and a substrate heating apparatus adapted to heat the substrate to which the HF gas is supplied.

The substrate processing system according to the third aspect realizes advantages similar to those attained by the substrate processing method according to the first aspect of this invention.

The substrate processing system can include a substrate transferring apparatus disposed between the plasma etching apparatus, the HF gas supply apparatus, and the substrate heating apparatus, the substrate transferring apparatus being adapted to transfer the substrate such that the substrate is not exposed to ambient air.

In that case, the substrate is not exposed to ambient air during the time it is etched by the plasma of the halogen-based gas, and the HF gas is supplied toward the substrate which is then heated. Therefore, it is unnecessary to manage the time period of exposure of the substrate to the ambient air.

In the substrate processing system, the HF gas supply apparatus and the substrate heating apparatus can each be constructed by the same apparatus.

With this substrate processing system, the HF gas supply apparatus and the substrate heating apparatus are each constructed by the same apparatus, and therefore, the substrate processing system can be downsized.

According to a fourth aspect of this invention, there is provided a substrate processing system for processing a substrate having a single-crystal silicon substrate base, a first oxide film formed by a thermal oxidation treatment, and a second oxide film containing an impurity, a part of the single-crystal silicon substrate base being exposed through the first and second oxide films, comprising a plasma etching apparatus adapted to etch the exposed single-crystal silicon substrate base using a plasma of a halogen-based gas, an HF gas supply apparatus adapted to supply an HF gas toward the substrate, and a cleaning gas supply apparatus adapted to supply a cleaning gas containing at least NH3gas toward the substrate to which the HF gas is supplied.

The substrate processing system according to the fourth embodiment can produce advantages similar to those attained by the substrate processing method according to the second embodiment of this invention.

The substrate processing system can include a substrate transferring apparatus disposed between the plasma etching apparatus, the HF gas supply apparatus, and the substrate heating apparatus, the substrate transferring apparatus being adapted to transfer the substrate such that the substrate is not exposed to ambient air.

In that case, while the substrate is being etched by the plasma of the halogen-based gas and the HF gas and the cleaning gas are being supplied toward the substrate, the substrate is not exposed to the ambient air, making it unnecessary to manage the time period of exposure of the substrate to the ambient air.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail below with reference to the drawings showing preferred embodiments thereof.

First, an explanation will be given of a substrate processing system according to a first embodiment of the present invention.

FIG. 1is a plan view schematically showing the construction of the substrate processing system of this embodiment.

As shown inFIG. 1, the substrate processing apparatus10is comprised of a transfer module11(substrate transferring apparatus) having a hexagonal shape as viewed in plan, two plasma process modules12,13(plasma etching apparatuses) connected to one side surface of the transfer module11, two plasma process modules14,15(plasma etching apparatuses) connected to another side surface of the transfer module11such as to face the plasma process modules12,13, a gas process module16(HF gas supply apparatus) disposed adjacent to the plasma process module13and connected to the transfer module11, a heating process module17(substrate heating apparatus) disposed adjacent to the plasma process module15and connected to the transfer module11, a loader module18which is a rectangular transfer chamber, and two load lock modules19,20disposed between the transfer module11and the loader module18for connecting them.

The transfer module11has disposed therein a transfer arm21that can bend/elongate and turn. The transfer arm21can transfer wafers W between the plasma process modules12to15, the gas process module16, the heating process module17, and the load lock modules19,20.

The plasma process module12to15each include a processing chamber for receiving a wafer W. Each plasma process module can introduce a halogen-based processing gas, for example an HBr gas, into the chamber and generate electric field in the chamber, thereby generating a plasma from the introduced processing gas. Using the plasma, the plasma process module can etch the wafer W. More specifically, a single-crystal silicon substrate base71of the wafer W shown inFIG. 7is etched.

FIG. 2Ais a section view showing the gas process module16inFIG. 1taken along line I-I inFIG. 1, andFIG. 2Bis an enlarged view showing an A portion inFIG. 2A.

As shown inFIG. 2A, the gas process module16includes a processing chamber22, a wafer-mounting stage23disposed within the chamber22, a shower head24disposed in an upper part of the chamber22such as to face the stage23, a TMP (turbo molecular pump)25afor exhausting a gas and the like out from the chamber22, and an APC (adaptive pressure control) valve25b, which is a variable butterfly valve, disposed between the chamber22and the TMP25a.

The shower head24is comprised of a disk-shaped gas supply unit26having a buffer chamber27formed therein. The buffer chamber27is communicated via gas-passing holes28with the inside of the chamber22, and is connected to an HF gas supply system (not shown) that can supply an HF gas to the buffer chamber27. The supplied HF gas is then supplied via the gas-passing holes28to the inside of the chamber22.

As shown inFIG. 2B, the gas-passing holes28formed in the shower head24each have a portion thereof opening into the chamber22and formed such as to widen out toward an end of the gas-passing hole. As a result, the HF gas can efficiently be diffused into the chamber22. Furthermore, the gas-passing holes28each have a constriction in its cross section, and therefore, any residual matter or the like produced in the chamber22can be prevented from flowing back into the gas-passing holes28and then into the buffer chamber27.

In the gas process module16, a heater (not shown), for example a heating element, is built in a side wall of the chamber22. By heating the side wall of the chamber22by the heating element, a residual matter produced when the BPSG film75and the deposit film76are removed using fluorinated acid can be prevented from being attached to the side wall of the chamber.

Moreover, the stage23has a coolant chamber (not shown) as a temperature adjusting mechanism, in which a coolant, for example cooling water or a Galden (registered trademark) fluid, at a predetermined temperature is circulated. The temperature of the wafer W attracted to and held on an upper surface of the stage23is controlled through the temperature of the coolant.

Referring toFIG. 1again, the heating process module17includes a processing chamber for receiving a wafer W. The chamber is provided with a halogen lamp, a sheet heater, or the like, and can heat the wafer W received therein.

The insides of the transfer module11, the plasma process modules12to15, the gas process module16, and the heating process module17can be depressurized. The transfer module11is connected via vacuum gate valves12ato17ato the plasma process modules12to15, the gas process module16, and the heating process module17.

In the substrate processing system10, the internal pressure in the transfer module11is held at vacuum, whereas that in the loader module18is held at atmospheric pressure. To this end, the load lock modules19,20are provided with vacuum gate valves19a,20aat connecting parts between themselves and the transfer module11, and provided with atmospheric gate valves19b,20bat connecting parts between themselves and the loader module18, whereby each load lock module is constructed as a preliminary vacuum transfer chamber whose internal pressure can be adjusted. The load lock modules19,20are further provided with wafer-mounting stages19c,20con each of which a wafer W delivered between the loader module18and the transfer module11can temporarily be placed.

In addition to the load lock modules19,20, there are connected to the loader module18three FOUP-mounting stages30each mounted with a FOUP (front opening unified pod)29, which is a container adapted to house twenty-five wafers W, an orienter31used for pre-alignment of a wafer W transferred out from a FOUP29, and first and second IMS's (integrated metrology systems manufactured by Therma-Wave, Inc.)32,33for measuring the surface state of the wafer W.

The load lock modules19,20are connected to a longitudinal side wall of the loader module18and disposed to face the three FOUP mounting stages30, with the loader module18interposed therebetween. The orienter31is disposed at a longitudinal one end of the loader module18, the first IMS32is disposed at another longitudinal end of the loader module18, and the second IMS33is disposed alongside the three FOUP mounting stages30.

The loader module18includes a SCARA-type dual arm transfer arm34disposed therein for transferring a wafer W, and three loading ports35formed in a side wall of the loader module18to correspond to the FOUP mounting stages30. The transfer arm34takes a wafer W out from the corresponding FOUP29on the FOUP mounting stage30through the loading port35, and transfers the removed wafer W into and out of the load lock modules19,20, the orienter31, the first IMS32, and the second IMS33.

The first IMS32is an optical monitor that has a mounting stage36adapted to be mounted with a wafer W transferred into the first IMS32, and an optical sensor37adapted to be directed to the wafer W mounted on the stage36. The first IMS32measures the surface shape of the wafer W, for example the film thickness of a surface layer thereof, and CD (critical dimension) values of wiring grooves, gate electrodes and so on formed therein. Like the first IMS32, the second IMS33is an optical monitor and has amounting stage38and an optical sensor39. The second IMS measures, for example, a number of particles on a surface of the wafer W.

The substrate processing system10is provided with an operation panel40disposed at a longitudinal one end of the loader module18. The operation panel40has a display section comprised of, for example, an LCD (liquid crystal display), for displaying the state of operation of component elements of the substrate processing system10.

To permit an apparatus for removing the BPSG film75and the deposit film76of a wafer W shown inFIG. 7to be installed on the substrate processing system10, the films75,76must be removed in a dry environment. The BPSG film75is a silicon-base oxide film, the deposit film76is a pseudo-SiO2film made of SiOBr, and the thermally-oxidized film72is an SiO2film. Therefore, there is a possibility that the thermally-oxidized film72can be removed when the BPSG film75and the deposit film76are removed. If the thermally-oxidized film72is removed, that part of the hole or the trench which corresponds to the film72can be caved in such that a notch is formed therein. Thus, the BPSG film75and the deposit film76must be removed at a high selectivity ratio to the thermally-oxidized film72.

To find a method capable of removing the BPSG film75and the deposit film76in a manner to satisfy the above described necessary conditions, the present inventors conducted various experiments. As a result, it was found that the BPSG film75and the deposit film76could be removed and the selectivity ratio of the films75,76to the film72could be increased up to 1000 by supplying only an HF gas to the wafer W, without supplying H2O gas, in an environment where substantially no H2O is present.

The present inventors further conducted extensive research on the mechanism of the above described removal method, and reached a tentative theory, which will be described below.

When an HF gas is combined with H2O, fluorinated acid is formed which erodes and removes an oxide film. In order to form fluorinated acid from the HF gas in an environment where there is substantially no H2O, the HF gas must be combined with water (H2O) molecules contained in the oxide film.

The BPSG film75is formed by vapor deposition such as CVD processing, and the deposit film76is formed by reaction between plasma and silicon. Thus, these films75,76are nondense in film structure and hence likely to be attached with water molecules. Thus, the BPSG film75and the deposit film76contain some water molecules. When the HF gas reaches the films75,76, the HF gas is combined with water molecules to form fluorinated acid, which erodes the films75,76. Thus, the BPSG film75and the deposit film76can be removed without using a chemical solution and plasma.

On the other hand, the thermally-oxidized film72is formed by a thermal oxidation treatment in an environment where the temperature is in the range from 800 to 900 degrees C. Thus, no water molecules are contained in the thermally-oxidized film72during the fabrication of the film. Besides, the thermally-oxidized film72is dense in film structure, and therefore, water molecules are less easily to be attached to the film72. As a result, the thermally-oxidized film72contains substantially no water molecules. Since water molecules are not present, even if the supplied HF gas reaches the film72, the HF gas does not form fluorinated acid and thus the thermally-oxidized film72is not eroded.

Accordingly, the selectivity ratio of the BPSG film75and the deposit film76to the thermally-oxidized film72can be increased (for example, up to 1000) and therefore, these films75,76can selectively be etched by supplying only the HF gas to the wafer, without H2O gas being supplied, in an environment where substantially no H2O is present.

When the BPSG film75and the deposit film76are removed using fluorinated acid, chemical reaction takes place between SiO2in the films75,76and fluorinated acid (HF) as represented by the following chemical formulae.
SiO2+4HF→SiF4+2H2O↑
SiF4+2HF→H2SiF6

In this way, there is produced a residual matter (H2SiF6). The residual matter can cause conduction failure of resultant semiconductor devices and thus must be removed.

In this embodiment, thermal energy is utilized to remove the residual matter. More specifically, a wafer W in which the residual matter has been produced is heated, thereby thermally decomposing the residual matter as represented by the following formula.
H2SiF6+Q(thermal energy)→2HF↑+SiF4↑

That is, in this embodiment, H2SiF6which is the residual matter formed as a result of reaction between SiO2and fluorinated acid is removed by heating.

Next, a substrate processing method of this embodiment will be described.

FIGS. 3A to 3Dare a process diagram showing the substrate processing method implemented by the substrate processing system shown inFIG. 1.

First, a thermally-oxidized film72, films73,74, and a BPSG film75are formed in layers on a single-crystal silicon substrate base71, thereby preparing a wafer W in which part of the single-crystal silicon substrate base71is exposed through the films72to75. Then, the wafer W is transferred into either one of the plasma process modules12to15. In the plasma process module into which the wafer W has been transferred, a hole or a trench is formed in the single-crystal silicon substrate base71of the wafer W using a plasma generated from an HBr gas (plasma etching step). At that time, a deposit film76is formed in the hole or the trench of the wafer W (FIG. 3A).

Next, the wafer W shown inFIG. 3Ais transferred out from the chamber of the plasma process module, and is transferred via the transfer module11into the chamber22of the gas process module16. Then, the wafer W is placed on the stage23. The pressure in the chamber22is set to 1.3×101to 1.1×103Pa (1 to 8 Torrs) using the APC valve25band the like, and the ambient temperature in the chamber22is set in the range from 40 to 60 degrees C. using the heater in the side wall of the chamber. Then, the HF gas is supplied toward the wafer W from the gas supply unit26of the shower head24at a flow rate ranging from 40 to 60 SCCM (HF gas supply step) (FIG. 3B). At that time, water molecules are nearly completely removed from inside the chamber22, and H2O gas is not supplied into the chamber22.

The HF gas reaching the BPSG film75and the deposit film76is combined with water molecules contained in the film75,76to thereby produce fluorinated acid. The fluorinated acid erodes the BPSG film75and the deposit film76. As a result, the films75,76are selectively etched. On the other hand, a residual matter41is produced as a result of chemical reaction between the fluorinated acid and SiO2in the BPSG film75and the deposit film76. In the hole or the trench, the residual matter41is deposited on the films73,74, the thermally-oxidized film72, and the single-crystal silicon substrate base71(FIG. 3C).

Next, the wafer W on which the residual matter41has been deposited is transferred out from the chamber22of the gas process module16, and is then transferred via the transfer module11into the chamber of the heating process module17. The heating process module17heats the wafer W transferred thereinto up to a predetermined temperature, specifically, to 150 degrees C. or higher (substrate heating step). The heating process module17introduces N2gas into the chamber thereof. The introduced N2gas forms a stream of gas in the chamber. At that time, H2SiF6forming the residual matter41is decomposed by heat into HF and SiF4. The resultant HF and SiF4are caught and removed by the stream of gas (FIG. 3D).

Next, the wafer W is transferred out from the chamber22of the heating process module17, whereupon the present process is completed.

According to the substrate processing method of this embodiment, the single-crystal silicon substrate base71of the wafer W that is partly exposed through the thermally-oxidized film72, the films73,74, and the BPSG film75is etched by the plasma of HBr gas, the HF gas is supplied toward the wafer W, and the wafer W is heated. When the single-crystal silicon substrate base71is etched by the plasma of HBr gas, a deposit film76is formed. Fluorinated acid generated from the HF gas selectively etches the deposit film76and the BPSG film75, and on the other hand, a residual matter41(H2SiF6) is generated. By being heated, the residual matter41is decomposed into HF and SiF4. As a result, the deposit film76and the BPSG film75can be removed in a dry environment. This makes it possible to dispose the gas process module16and the heating process module17in one substrate processing system10. Thus, after the single-crystal silicon substrate base71of the wafer W has been etched, the wafer W can be transferred via the transfer module11into the gas process module16or the heating process module17. Therefore, without the wafer W being exposed to the atmospheric air, the deposit film76and the BPSG film75of the wafer W can be removed, making it possible to simplify the substrate processing process and eliminate the need of managing a time period during which the wafer W is exposed. As a result, it is possible to prevent a reduction in the productivity of the fabrication of a semiconductor device from the wafer W.

With the above described substrate processing method, the gas process module16and the heating process module17can be disposed in one substrate processing system10. Thus, it is unnecessary to dispose the gas process module16and the heating process module17at different places, making it possible to reduce a system installation area (footprint).

Furthermore, with the above described substrate processing method, the wafer W is heated in N2gas ambient. The N2gas forms a stream of gas that catches and transfers the residual matter41decomposed by being heated, thereby ensuring that the deposit film76and the BPSG film75are removed.

Furthermore, with the above described substrate processing method, the HF gas is supplied toward the wafer W having the BPSG film75and the deposit film76formed thereon. The HF gas is combined with water molecules contained in the BPSG film75and the deposit film76to form fluorinated acid that erodes and selectively etches the films75,76. Therefore, at the time of removal of the films75,76, the thermally-oxidized film72is prevented from being removed, whereby formation of a notch can be prevented.

In the above described substrate processing system10, the gas process module16and the heating process module17are provided as independent apparatuses. Alternatively, as shown inFIG. 4, there may be provided a stage heater43having a stage23in which a gas process module42is incorporated, wherein the stage heater43can heat a wafer W placed on the stage23. In that case, with use of only the gas process module42, the BPSG film75and the deposit film76can selectively be etched and the residual matter41can thermally be decomposed. Thus, both the functions of the gas process module and the thermal process module can be realized by means of one process module, making it possible to downsize the substrate processing system10.

Next, a substrate processing system according to a second embodiment of this invention will be described.

This embodiment is basically the same in construction and function as the first embodiment, and only differs therefrom in that this embodiment does not utilize thermal decomposition of residual matter. In the following, constructions and functions of this embodiment that are different from those of the first embodiment will be explained, with explanations on the same or similar construction omitted.

As described in the above, when the BPSG film75and the deposit film76are removed using fluorinated acid, chemical reaction takes place between the fluorinated acid and the BPSG film75or the deposit film76, to produce a residual matter41(H2SiF6). In this embodiment, NH3is used to remove the residual matter41. More specifically, NH3gas is supplied toward the residual matter to cause chemical reaction represented by the following formula.
H2SiF6+2NH3→2NH4F+SiF4↑

In this way, there are generated NH4F (ammonium fluoride) and SiF4. The NH4F is a product of chemical reaction, which can be sublimated. By setting an ambient temperature somewhat higher than a room temperature, the NH4F can be sublimated and therefore can easily be removed.

In this embodiment, therefore, the H2SiF6, which is a residual matter produced by chemical reaction between SiO2and fluorinated acid, is removed by causing chemical reaction between H2SiF6and NH3and sublimation of NH4F.

The substrate processing system of this embodiment is the same in construction as the substrate processing system10shown inFIG. 1. Instead of the gas process module16and the heating process module17, there is provided the gas process module44(HF gas supply apparatus and cleaning gas supply apparatus) for selectively etching the BPSG film75and the deposit film76, for causing chemical reaction between the residual matter41and NH3, and for causing sublimation of a product of the chemical reaction (NH4F). The gas process module44is connected via a vacuum gate valve44ato the transfer module11.

FIG. 5is a section view showing the gas process module44of the substrate processing system of this embodiment.

InFIG. 5, the gas process module44includes a chamber22, a stage23, a shower head45, a TMP25a, and an APC valve25b.

The shower head45is comprised of a disk-shaped lower gas supply section46and an upper gas supply section47which is stacked on the lower gas supply section46. The lower and upper gas supply sections46,47have first and second buffer chambers48,49, respectively. The first and second buffer chambers48,49are respectively communicated via gas-passing holes50,51to the inside of the chamber22.

The first buffer chamber48is communicated with an NH3(ammonia) gas supply system (not shown), which can supply the first buffer48with an NH3-containing gas (cleaning gas). The supplied cleaning gas is supplied via gas-passing holes50to the inside of the chamber22. The second buffer chamber49is connected to an HF gas supply system, which can supply the second buffer chamber49with an HF gas. The supplied HF gas is then supplied via gas-passing holes51to the inside of the chamber22.

Like the gas-passing holes28shown inFIG. 2B, each of the gas-passing holes50,51is formed to have a portion thereof opening out into the chamber22and formed to widen out toward an end thereof, whereby the cleaning gas and the HF gas can efficiently be diffused into the chamber22. Furthermore, each of the gas-passing holes50,51has a cross-sectional shape having a constriction therein, whereby the residual matter or the like generated in the chamber22can be prevented from flowing back into the gas-passing holes50,51and then into the first and second buffer chambers48,49.

In the gas process module44, a heater (not shown), for example a heating element, is built into a side wall of the chamber22. As a result, it is possible to set the ambient temperature in the chamber22to be higher than a room temperature, thereby promoting sublimation of NH4F described later.

Next, an explanation will be given of a substrate processing method according to this embodiment.

FIGS. 6A to 6Eare a process diagram showing the substrate processing method implemented by the substrate processing system of this embodiment.

Like the case shown inFIG. 3A, a wafer W is first transferred into either one of the plasma process modules12to15. In the plasma process module into which the wafer W has been transferred, a hole or a trench is formed in the single-crystal silicon substrate base71of the wafer W using a plasma generated from the HBr gas (plasma etching step). At that time, a deposit film76is formed in the hole or trench in the wafer W (FIG. 6A).

Next, the wafer W shown inFIG. 6Ais transferred out from the plasma process module, and is then transferred via the transfer module11into the chamber22of the gas process module44. The wafer W is placed on the stage23. The pressure within the chamber22, the ambient temperature within the chamber22, the flow rate at which the HF gas is supplied from the upper gas supply section47are set in a manner similar to in the case shown inFIG. 3B(HF gas supply step). As with the case shown inFIG. 3B, water molecules are nearly completely removed from within the chamber22, and no H2O gas is supplied to the chamber22.

As with the case shown inFIG. 3C, a residual matter41is produced by chemical reaction between fluorinated acid and SiO2contained in the BPSG film75and the deposit film76, and is deposited on the films73,74, the thermally-oxidized film72, and the single-crystal silicon substrate base71in the hole or the trench (FIG. 6C).

Next, the HF gas supply to the chamber22is terminated. Thereafter, a cleaning gas is supplied from the lower gas supply section46of the shower head45toward the wafer W (cleaning gas supply step) (FIG. 6D). At that time, NH3gas contained in the cleaning gas reacts with H2SiF6constituting the residual matter41to produce NH4F and SiF4. Then, the ambient temperature within the chamber22is set to be somewhat higher than the room temperature using the heating element in the side wall of the chamber, whereby the NH4F is sublimated (FIG. 6E).

Next, the wafer W is transferred out from the chamber22of the gas process module44, and the present process is terminated.

According to the substrate processing method of this embodiment, part of the single-crystal silicon substrate base71of the wafer W is exposed through the thermally-oxidized film72, the films73,74, and the BPSG film75and is etched by the plasma of HBr gas, the HF gas is supplied toward the wafer W, and the cleaning gas containing NH3gas is supplied toward the wafer W. When the single-crystal silicon substrate base71is etched by the plasma of HBr gas, a deposit film76is formed. Fluorinated acid generated from the HF gas selectively etches the deposit film76and the BPSG film75, and produces a residual matter41. The NH3gas reacts with the residual matter41to produce a product of chemical reaction (NH4F) which is easily sublimated. The reaction product is easily sublimated when the ambient temperature in the chamber22is set to be somewhat higher than the room temperature. In other words, the deposit film76and the BPSG film75can be removed in a dry environment. This makes it possible to install the gas process module44in the substrate processing system10. Accordingly, after the single-crystal silicon substrate base71of the wafer is etched, the wafer W can be transferred via the transfer module11into the gas process module44. Thus, after the single-crystal silicon substrate base71has been etched, the deposit film76and the BPSG film75can be removed without the wafer W being exposed to the atmospheric air. This makes it possible to simplify the substrate processing process and eliminate the need of managing a time period of exposure of the wafer W, whereby a reduction in productivity of the fabrication of a semiconductor device from the wafer W can be prevented.

Since the above described substrate processing method permits the gas process module44to be installed on the substrate processing system, it is unnecessary to install the gas process module44at a location different from the system, thus making it possible to reduce a footprint of the entire system.

Since the above described substrate processing method can realize the selective etching of the BPSG film75and the deposit film76and the removal of the residual matter41only by use of the gas process module44, the substrate processing system10can be downsized.

It should be noted that the selective etching of the BPSG film75and the deposit film76, the generation of the reaction product from the residual matter41, and the sublimation of the reaction product may be realized using different process modules.

In the above described embodiments, the BPSG film75is used as a hard mask. However, the oxide film used as the hard mask is not limited thereto, but may be one that contains a higher impurity content at least than in the thermally-oxidized film72. Specifically, there may be provided a TEOS (tetra ethyl ortho silicate) film or a BSG (boron silicate glass) film. The residual matter to be removed is not limited to H2SiF6. The present invention is applicable to the removal of any residual matter that is generated at the time of removal of oxide films using fluorinated acid.

It is to be understood that the present invention can also be attained by supplying a computer with a storage medium in which a program code of software that realizes the functions of the embodiments described above is stored, and then causing the computer to read out and execute the program code stored in the storage medium.

In this case, the program code itself read out from the storage medium realizes the functions of the embodiments described above, and hence the program code and the storage medium in which the program code is stored constitute the present invention.

The storage medium for supplying the program code may be, for example, a floppy (registered trademark) disk, a hard disk, a magnetic-optical disk, an optical disk such as a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, a DVD-RW, or a DVD+RW, a magnetic tape, a non-volatile memory card, or a ROM. Alternatively, the program may be downloaded via a network from another computer, a database, or the like, not shown, connected to the Internet, a commercial network, a local area network, or the like.

Moreover, it is to be understood that the functions of the embodiments can be accomplished not only by executing a program code read out by the computer, but also by causing an OS (operating system) or the like which operates on the computer to perform a part or all of the actual operations based on instructions of the program code.

Furthermore, it is to be understood that the functions of the embodiments can also be accomplished by writing a program code read out from a storage medium into a memory provided on an expansion board inserted into the computer or in an expansion unit connected to the computer and then causing a CPU or the like provided on the expansion board or in the expansion unit to perform a part or all of the actual operations based on instructions of the program code.

The form of the program code may be an object code, a program code executed by an interpreter, script data supplied to an OS, or the like.