JP2008010661A - Method and apparatus for processing substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate processing method capable of selectively removing a nitride film. <P>SOLUTION: In a wafer W having a thermal oxidation film 51 made of SiO<SB>2</SB>and a nitride silicon film 52 made of SiN, oxygen plasma formed by plasmizing an oxygen gas is allowed to contact the silicon nitride film 52 to change the silicon nitride film 52 into a silicon monoxide film 54, an HF gas is supplied to the silicon monoxide film 54 to selectively etch the silicon monoxide film 54 using a hydrofluoric acid to be generated from the HF gas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a substrate processing method and a substrate processing apparatus, and more particularly to a substrate processing method for processing a substrate on which a thermal oxide film and a silicon nitride film are formed.

  2. Description of the Related Art A semiconductor device wafer (substrate) having a thermal oxide film formed by a thermal oxidation process, for example, a silicon oxide film and a silicon nitride film formed by a CVD process or the like is known. The silicon nitride film is used as an antireflection (BARC) film or a spacer that separates the gate and the source / drain. The thermal oxide film forms a gate oxide film.

As a method for etching a silicon nitride film, a compound gas containing fluorine as a constituent element and not carbon as a constituent element, for example, a compound gas containing HF gas, is plasmatized, and the plasmatized compound gas is reacted with carbon to generate chemical species (radicals). ) And etching the silicon nitride film with chemical species is known (see, for example, Patent Document 1).
JP 2003-264183 A

  However, the chemical species also etch the thermal oxide film. For example, in a wafer in which a silicon oxide film (thermal oxide film) is formed as a gate insulating film on a silicon substrate and a silicon nitride film as an antireflection film is further formed on the silicon oxide film, the above etching method is used. Not only the silicon nitride film but also the silicon oxide film is etched. Here, since the gate insulating film is usually formed thinner than the antireflection film, the silicon oxide film is removed before the silicon nitride film is removed, resulting in damage to the silicon substrate. (Etching).

  An object of the present invention is to provide a substrate processing method and a substrate processing apparatus capable of selectively removing a nitride film.

  In order to achieve the above object, a substrate processing method according to claim 1 is a substrate processing method for processing a substrate having a thermal oxide film and a nitride film formed by a thermal oxidation process, wherein the substrate contains oxygen. An oxygen plasma contact step for contacting plasma and an HF gas supply step for supplying HF gas toward the substrate in contact with the plasma containing oxygen are characterized.

  The substrate processing method according to claim 2 is the substrate processing method according to claim 1, wherein the substrate includes a convex conductive portion protruding on the thermal oxide film, and the nitride film has side surfaces and tops of the conductive portion. In the oxygen plasma contact step, the active species in the plasma containing oxygen moves substantially parallel to the side surface and contacts the nitride film.

  A substrate processing method according to a third aspect is the substrate processing method according to the second aspect, wherein the active species includes at least a cation.

  A substrate processing method according to a fourth aspect of the present invention is the substrate processing method according to the second or third aspect, further comprising a selective oxidation step of selectively oxidizing the flat portion of the nitride film.

  The substrate processing method according to claim 5 is the substrate processing method according to claim 1, wherein the substrate includes a convex conductive portion that protrudes perpendicularly from the surface of the substrate on the thermal oxide film, and the nitride film includes: The side surface and top surface of the conductive portion are covered, and in the oxygen plasma contact step, active species in the plasma containing oxygen move substantially perpendicular to the surface of the substrate and contact the nitride film. And

  The substrate processing method according to claim 6 is the substrate processing method according to claim 5, further comprising a selective oxidation step of selectively oxidizing the flat portion of the nitride film.

  In order to achieve the above object, a substrate processing apparatus according to claim 7 is a substrate processing apparatus for processing a substrate having a thermal oxide film and a nitride film formed by a thermal oxidation process, wherein the substrate includes plasma containing oxygen. An oxygen plasma contact device to be contacted and an HF gas supply device for supplying HF gas toward the substrate in contact with the plasma containing oxygen are provided.

  According to the substrate processing method of claim 1 and the substrate processing apparatus of claim 3, the plasma containing oxygen contacts the substrate having a thermal oxide film and a nitride film formed by thermal oxidation, and the substrate HF gas is supplied toward The plasma containing oxygen changes the nitride film into an oxide film, and the hydrofluoric acid generated from the HF gas selectively etches the oxide film changed from the nitride film. Therefore, the nitride film can be selectively removed.

  According to the substrate processing method of claim 2, the active species in the plasma containing oxygen moves substantially parallel to the side surface toward the nitride film covering the side surface and the top surface of the conductive portion, and the active species are The nitride film is changed into an oxide film by contact. Since the thickness of the portion covering the side surface of the conductive portion in the nitride film along the moving direction of the active species is large, the active species cannot sufficiently enter the portion covering the side surface of the conductive portion. As a result, a nitride film that does not change to an oxide film remains on the side surface of the conductive portion. The hydrofluoric acid generated from the HF gas selectively etches the oxide film changed from the nitride film, but does not etch the nitride film. Therefore, other portions of the nitride film can be selectively removed without removing the portions covering the side surfaces of the conductive portions.

  According to the substrate processing method of the third aspect, the active species includes at least a cation. The sheath generated in the space near the surface of the substrate when plasma is generated accelerates positive ions toward the surface of the substrate. Therefore, the cation can be reliably brought into contact with the nitride film on the substrate.

  According to the substrate processing method of the fourth aspect, the flat portion of the nitride film is selectively oxidized. The hydrofluoric acid generated from the HF gas selectively etches the oxide film changed from the nitride film. Therefore, the flat portion of the nitride film can be selectively removed.

  According to the substrate processing method of claim 5, the active species in the plasma containing oxygen is applied to the surface of the substrate toward the nitride film covering the side surface and the top surface of the convex conductive portion protruding vertically from the surface of the substrate. In contrast, the active species contacts the nitride film and changes the nitride film into an oxide film. Since the thickness of the portion of the nitride film covering the side surface of the conductive portion along the direction perpendicular to the surface of the substrate is large, the active species that move substantially perpendicular to the surface of the substrate is sufficiently in the portion covering the side surface of the conductive portion. I cannot enter. As a result, a nitride film that does not change to an oxide film remains on the side surface of the conductive portion. The hydrofluoric acid generated from the HF gas selectively etches the oxide film changed from the nitride film, but does not etch the nitride film. Therefore, other portions of the nitride film can be selectively removed without removing the portions covering the side surfaces of the conductive portions.

  According to the substrate processing method of the sixth aspect, the flat portion of the nitride film is selectively oxidized. The hydrofluoric acid generated from the HF gas selectively etches the oxide film changed from the nitride film. Therefore, the flat portion of the nitride film can be selectively removed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, a substrate processing system that executes a substrate processing method according to a first embodiment of the present invention will be described.

  FIG. 1 is a plan view showing a schematic configuration of a substrate processing system for executing a substrate processing method according to the present embodiment.

  In FIG. 1, a substrate processing system 10 (substrate processing apparatus) includes a first process ship 11 for performing plasma processing on a semiconductor device wafer (hereinafter simply referred to as “wafer”) W (substrate), and the first process ship 11. A second process ship 12 which is arranged in parallel with the process ship 11 and is subjected to a selective etching process to be described later on the wafer W which has been subjected to the plasma process in the first process ship 11, and the first process ship 11 and the first process ship 11. And a loader module 13 as a rectangular common transfer chamber to which two process ships 12 are connected.

  In addition to the first process ship 11 and the second process ship 12 described above, a FOUP (Front Opening Unified Pod) 14 as a container for accommodating 25 wafers W is mounted on the loader module 13 3 Two hoop mounting tables 15, an orienter 16 that pre-aligns the position of the wafer W carried out of the hoop 14, and first and second IMS (Integrated Metrology System, Therma-Wave, Inc.) that measure the surface state of the wafer W. .) 17 and 18 are connected.

  The first process ship 11 and the second process ship 12 are connected to the side wall along the longitudinal direction of the loader module 13 and are disposed so as to face the three hoop mounting tables 15 with the loader module 13 interposed therebetween. 16 is disposed at one end in the longitudinal direction of the loader module 13, the first IMS 17 is disposed at the other end in the longitudinal direction of the loader module 13, and the second IMS 18 is disposed in parallel with the three hoop mounting tables 15.

  The loader module 13 serves as an inlet for a wafer W disposed on the side wall so as to correspond to the scalar type dual arm type transport arm mechanism 19 for transporting the wafer W and the respective hoop mounting tables 15. And three load ports 20. The transfer arm mechanism 19 takes out the wafer W from the FOUP 14 placed on the FOUP placement table 15 via the load port 20, and removes the taken wafer W from the first process ship 11, the second process ship 12, and the orienter 16. , Carry in / out to the first IMS 17 and the second IMS 18.

  The first IMS 17 is a monitor of the optical system, and includes a stage 21 on which the loaded wafer W is placed, and an optical sensor 22 that directs the wafer W placed on the stage 21. The shape, for example, the thickness of the polysilicon film, the CD (Critical Dimension) value of the wiring trench, the gate electrode, etc. is measured. The second IMS 18 is also an optical system monitor, and has a stage 23 and an optical sensor 24 as in the first IMS 17.

  The first process ship 11 includes a first process module 25 (oxygen plasma contact apparatus) that performs plasma processing on the wafer W, and a link type single pick type first that delivers the wafer W to the first process module 25. And a first load / lock module 27 having a built-in transfer arm 26 therein.

  The first process module 25 includes a cylindrical processing chamber container (chamber), and an upper electrode and a lower electrode (both not shown) disposed in the chamber, and the first process module 25 is provided between the upper electrode and the lower electrode. Is set to an appropriate interval for performing plasma processing on the wafer W. Further, the lower electrode has an ESC 28 at the top thereof for chucking the wafer W by Coulomb force or the like.

  In the first process module 25, oxygen gas is introduced into the chamber, and an oxygen electric field is generated by generating an electric field between the upper electrode and the lower electrode to generate oxygen plasma. Plasma treatment is performed by bringing the active species contained, specifically, cations into contact with the wafer W.

  In the first process ship 11, the internal pressure of the loader module 13 is maintained at atmospheric pressure, while the internal pressure of the first process module 25 is maintained at vacuum. Therefore, the first load / lock module 27 includes a vacuum gate valve 29 at the connection portion with the first process module 25 and an atmospheric gate valve 30 at the connection portion with the loader module 13. It is configured as a vacuum preparatory transfer chamber that can adjust the pressure.

  Inside the first load / lock module 27, a first transfer arm 26 is installed at a substantially central portion, and a first buffer 31 is installed on the first process module 25 side from the first transfer arm 26. The second buffer 32 is installed on the loader module 13 side from the first transfer arm 26. The first buffer 31 and the second buffer 32 are arranged on the trajectory on which the support portion (pick) 33 supporting the wafer W arranged at the tip portion of the first transfer arm 26 moves, and the plasma processing has been completed. By temporarily retracting the wafer W above the track of the support portion 33, the unprocessed wafer W and the processed wafer W can be smoothly exchanged in the first process module 25.

  The second process ship 12 is connected to a second process module 34 that performs a selective etching process to be described later on the wafer W, and is connected to the second process module 34 via a vacuum gate valve 35. And a second load / lock module 37 having a second transfer arm 36 of a link type single pick type for delivering the wafer W to the module 34.

  2 is a cross-sectional view of the second process module in FIG. 1, FIG. 2 (A) is a cross-sectional view along line II in FIG. 1, and FIG. 2 (B) is in FIG. 2 (A). It is an enlarged view of the A section.

  In FIG. 2A, the second process module 34 includes a cylindrical processing chamber container (chamber) 38, a mounting table 39 for the wafer W disposed in the chamber 38, and a mounting table above the chamber 38. 39, a shower head 40 disposed so as to be opposed to 39, a TMP (Turbo Molecular Pump) 41 for exhausting gas in the chamber 38, and the chamber 38 and the TMP 41, and controls the pressure in the chamber 38. And an APC (Adaptive Pressure Control) valve 42 as a variable butterfly valve.

  The shower head 40 has a disk-shaped gas supply unit 43 (HF gas supply device), and the gas supply unit 43 has a buffer chamber 44. The buffer chamber 44 communicates with the chamber 38 through the gas vent 45.

  The buffer chamber 44 in the gas supply unit 43 of the shower head 40 is connected to an HF gas supply system (not shown). The HF gas supply system supplies HF gas to the buffer chamber 44. The supplied HF gas is supplied into the chamber 38 through the gas vent 45. The gas supply unit 43 of the shower head 40 incorporates a heater (not shown), for example, a heating element. This heating element controls the temperature of the HF gas in the buffer chamber 44.

  In the shower head 40, as shown in FIG. 2B, the opening into the chamber 38 in the gas vent hole 45 is formed in a divergent shape. Thereby, HF gas can be efficiently diffused into the chamber 38. Further, since the gas vent hole 45 has a constricted cross section, the residue generated in the chamber 38 is prevented from flowing back to the gas vent hole 45 and then to the buffer chamber 44.

  In the second process module 34, the side wall of the chamber 38 incorporates a heater (not shown), for example, a heating element. Thereby, the atmospheric temperature in the chamber 38 can be set higher than normal temperature, and the removal of the silicon monoxide film 54 described later with hydrofluoric acid can be promoted. The heating element in the side wall prevents the residue generated when removing the silicon monoxide film 54 with hydrofluoric acid from adhering to the inside of the side wall by heating the side wall.

  The mounting table 39 has a refrigerant chamber (not shown) inside as a temperature control mechanism. A coolant having a predetermined temperature, for example, cooling water or a Galden solution, is supplied to the coolant chamber, and the temperature of the wafer W mounted on the upper surface of the mounting table 39 is controlled by the temperature of the coolant.

  Returning to FIG. 1, the second load / lock module 37 has a housing-like transfer chamber (chamber) 46 in which the second transfer arm 36 is built. The internal pressure of the loader module 13 is maintained at atmospheric pressure, while the internal pressure of the second process module 34 is maintained at atmospheric pressure or lower, for example, approximately vacuum. Therefore, the second load / lock module 37 is provided with a vacuum gate valve 35 at the connection portion with the second process module 34 and an atmospheric door valve 47 at the connection portion with the loader module 13, thereby increasing the internal pressure. It is configured as a vacuum preliminary transfer chamber that can be adjusted.

  In addition, the substrate processing system 10 includes an operation panel 48 disposed at one end in the longitudinal direction of the loader unit 13. The operation panel 48 includes a display unit made up of, for example, an LCD (Liquid Crystal Display), and the display unit displays the operation status of each component of the substrate processing system 10.

By the way, as a method for selectively etching an oxide film containing an impurity in a wafer having a thermal oxide film formed by a thermal oxidation process and an oxide film containing an impurity formed by a CVD process, for example, HF gas, Alternatively, a method is known in which a mixed gas of HF gas and H ₂ O gas is used without being converted into plasma (see, for example, JP-A-06-181188).

In addition, the present inventor conducted various experiments in order to increase the selectivity of the oxide film containing impurities to the thermal oxide film as compared with the above method. As a result, in an environment where almost no H ₂ O exists, the H ₂ O gas It has been found that when only the HF gas is supplied toward the wafer W without supplying oxygen, the selectivity of the oxide film containing impurities to the thermal oxide film can be greatly increased.

  And this inventor earnestly researched about the mechanism of said high selection ratio realization, and came to analogize the hypothesis demonstrated below.

The HF gas becomes hydrofluoric acid when combined with H ₂ O, and the hydrofluoric acid invades and removes the oxide film. Here, in order that the HF gas becomes hydrofluoric acid in an environment in which almost no H ₂ O exists, it is necessary to be associated with water (H ₂ O) molecules contained in the oxide film.

  Since the oxide film containing impurities is formed by vapor deposition such as a CVD process, the structure of the film is sparse and water molecules are easily adsorbed. Therefore, the oxide film containing impurities contains water molecules to some extent. The HF gas that reaches the oxide film containing impurities is combined with the water molecules to form hydrofluoric acid. This hydrofluoric acid invades the oxide film containing impurities.

  On the other hand, since the thermal oxide film is formed by a thermal oxidation process in an environment of 800 to 900 ° C., it does not contain water molecules at the time of film formation, and the film structure is dense, so that water molecules are adsorbed. Hateful. Therefore, the thermal oxide film contains almost no water molecules. Even if the supplied HF gas reaches the thermal oxide film, it does not become hydrofluoric acid because there is no water molecule. As a result, the thermal oxide film is not attacked.

As a result, when only HF gas is supplied toward the wafer W without supplying H ₂ O gas in an environment where almost no H ₂ O exists, the selectivity of the oxide film containing impurities to the thermal oxide film is greatly increased. (Selective etching process).

In this embodiment, on a silicon substrate 50 as shown in FIG. 3A, a thermal oxide film 51 made of SiO ₂ formed by a thermal oxidation process and a silicon nitride made of SiN formed by a CVD process. In the wafer W on which the film 52 (nitride film) is stacked, the selective etching process using hydrofluoric acid described above is used to selectively remove the silicon nitride film 52. Specifically, after the silicon nitride film 52 on the wafer W is changed to an oxide film by an oxidation process, the above-described selective etching process using hydrofluoric acid is used.

  Hereinafter, the oxidation treatment of the silicon nitride film 52 in the present embodiment will be described.

When the silicon nitride film 52 is brought into contact with an active species 53 in oxygen plasma (O ₂ plasma) generated from oxygen (O ₂ ) gas, for example, a cation (FIG. 3B), the silicon nitride film 52 SiN and the active species in the oxygen plasma cause a chemical reaction represented by the following formula:
2SiN + O ₂ → 2SiNO
SiNO is generated. Since SiNO is an unstable substance, as shown in the following formula, nitrogen is separated and sublimated,
2SiNO → 2SiO + N ₂ ↑
SiO (silicon monoxide) is produced. Thereby, the silicon nitride film 52 is changed to a silicon monoxide film 54 made of SiO (FIG. 3C). Since the silicon monoxide film 54 is formed by a CVD process and the silicon nitride film 52 having a sparse film structure is changed, the film structure of the silicon monoxide film 54 is also sparse. Therefore, the silicon monoxide film 54 contains water molecules to some extent. In the present embodiment, the silicon monoxide film 54 is selectively etched using a selective etching process using hydrofluoric acid, and as a result, the silicon nitride film 52 is selectively removed.

  Next, the substrate processing method according to the present embodiment will be described. The substrate processing method according to the present embodiment is executed by the substrate processing system 10 of FIG.

First, a wafer W is prepared in which a thermal oxide film 51 made of SiO ₂ is formed on a silicon substrate 50 and a silicon nitride film 52 made of SiN is formed on the thermal oxide film 51 (FIG. 3A). )). Then, the wafer W is loaded into the chamber of the first process module 25 and placed on the ESC 28.

  Next, oxygen gas is introduced into the chamber, and an electric field is generated between the upper electrode and the lower electrode, whereby the oxygen gas is turned into plasma to generate active species 53 in the oxygen plasma. Contact with the silicon nitride film 52 (oxygen plasma contact step). At this time, the sheath 55 is generated parallel to the surface of the wafer W in a space near the surface of the wafer W due to the electric field. Since a potential difference is generated in the sheath 55 along the direction perpendicular to the surface of the wafer W, the active species 53 such as cations in the oxygen plasma passing through the sheath 55 are made to the surface of the wafer W by the sheath 55. It is accelerated in the vertical direction. As a result, the active species 53 in the oxygen plasma comes into perpendicular contact with the silicon nitride film 52 formed on the surface of the wafer W (FIG. 3B). The active species 53 in the oxygen plasma in contact with the silicon nitride film 52 changes the silicon nitride film 52 into the silicon monoxide film 54 as described above (FIG. 3C).

  Next, the wafer W is unloaded from the chamber of the first process module 25 and loaded into the chamber 38 of the second process module 34 via the loader module 13. At this time, the wafer W is mounted on the mounting table 39.

Next, the pressure in the chamber 38 is set to 1.3 × 10 ^{1 to} 1.1 × 10 ³ Pa ( ^{1 to} 8 Torr) by the APC valve 42 or the like, and the atmospheric temperature in the chamber 38 is set to 40 to 40 by the heater in the side wall. Set to 60 ° C. Then, HF gas is supplied from the gas supply unit 43 of the shower head 40 toward the wafer W at a flow rate of 40 to 60 SCCM (HF gas supply step) (FIG. 3D). At this time, water molecules are substantially removed from the chamber 38 and no H ₂ O gas is supplied into the chamber 38.

  As described above, the silicon monoxide film 54 contains water molecules to some extent, and the HF gas that has reached the silicon monoxide film 54 is combined with the water molecules contained in the silicon monoxide film 54 to become hydrofluoric acid. Then, this hydrofluoric acid removes the silicon monoxide film 54. On the other hand, even if the HF gas reaches the thermal oxide film 51 after the silicon monoxide film 54 is removed by hydrofluoric acid and the thermal oxide film 51 is exposed, the thermal oxide film 51 contains almost no water molecules. HF gas hardly becomes hydrofluoric acid, and the thermal oxide film 51 is hardly removed. As a result, the silicon monoxide film 54 is selectively etched and removed (FIG. 3E).

  Next, the wafer W is unloaded from the chamber 38 of the second process module 34, and this process is completed.

  According to the substrate processing method according to the present embodiment, the active species 53 in the oxygen plasma comes into contact with the wafer W having the thermal oxide film 51 and the silicon nitride film 52, and HF gas is supplied toward the wafer W. Is done. The active species 53 in the oxygen plasma changes the silicon nitride film 52 into the silicon monoxide film 54, and the hydrofluoric acid generated from the HF gas selectively etches the silicon monoxide film 54 changed from the silicon nitride film 52. Therefore, the silicon nitride film 52 can be selectively removed.

In the substrate processing method described above, when HF gas is supplied toward the wafer W, water molecules are substantially removed from the chamber 38, and H ₂ O gas is not supplied into the chamber 38. In the thermal oxide film 51 that is not included, the HF gas and water molecules are hardly combined, and hydrofluoric acid is hardly generated, so that the oxide film 51 is hardly removed. Therefore, the silicon monoxide film 54 can be selectively etched more reliably.

Further, in the above-described substrate processing method, water molecules are almost removed from the chamber 38, H ₂ O gas is not supplied into the chamber 38, and is further included in the silicon monoxide film 54 on the wafer W. Water molecules are consumed by the reaction between SiO ₂ and hydrofluoric acid. Therefore, the inside of the chamber 38 can be maintained in a very dry state. As a result, generation of particles caused by water molecules and a watermark on the wafer W can be suppressed, and the reliability of a semiconductor device manufactured from the wafer W can be further improved.

  Next, a substrate processing method according to the second embodiment of the present invention will be described.

  This embodiment is basically the same in configuration and operation as the above-described first embodiment, and only the configuration of the substrate to be processed is different from that in the above-described first embodiment. Therefore, the description of the same configuration is omitted, and only the configuration and operation different from the first embodiment will be described below.

  FIG. 4 is a process diagram showing the substrate processing method according to the present embodiment.

First, a thermal oxide film 61 made of SiO ₂ is uniformly formed on a silicon substrate 60, and a gate electrode 62 (made of polysilicon having a substantially rectangular cross section protruding vertically from the surface of the wafer W ′ in the thermal oxide film 61 ( A wafer W ′ in which a convex conductive portion is formed and a silicon nitride film 63 made of SiN is formed on the thermal oxide film 61 is prepared. In this wafer W ′, the silicon nitride film 63 covers not only the thermal oxide film 61 but also the side and top surfaces of the gate electrode 62 (FIG. 4A). Then, the wafer W ′ is loaded into the chamber of the first process module 25 and placed on the ESC 28.

  Next, oxygen gas is introduced into the chamber, and an electric field is generated between the upper electrode and the lower electrode, whereby the oxygen gas is turned into plasma to generate active species 53 in the oxygen plasma. Contact with the silicon nitride film 63 (oxygen plasma contact step). At this time, as in the first embodiment, the sheath 55 is generated in a space near the surface of the wafer W ′ in parallel with the surface of the wafer W ′.

  The active species 53 such as cations in the oxygen plasma passing through the sheath 55 are accelerated by the sheath 55 in the vertical direction with respect to the surface of the wafer W ′ and moved along the vertical direction. Since the vertical direction with respect to the surface of the wafer W ′ is parallel to the side surface of the gate electrode 62, the active species 53 in the oxygen plasma that has passed through the sheath 55 moves substantially parallel to the side surface of the gate electrode 62, and forms the silicon nitride film 63. It contacts vertically (FIG. 4B).

  The active species 53 in the oxygen plasma in contact with the silicon nitride film 63 changes the silicon nitride film 63 into the silicon monoxide film 64 as described above, but the portion of the silicon nitride film 63 that covers the side surface of the gate electrode 62 is used. Since the thickness along the moving direction of the active species 53 (the direction perpendicular to the surface of the wafer W ′) is large, the active species 53 in the oxygen plasma cannot sufficiently enter the portion covering the side surface of the gate electrode 62. As a result, a nitrided portion 63a that does not change to the silicon monoxide film 64 remains on the side surface of the gate electrode 62 (FIG. 4C). On the other hand, a flat portion covering the top surface of the gate electrode 62 and a flat portion not covering the gate electrode 62 in the silicon nitride film 63 are changed to the silicon monoxide film 64 by the active species 53 in the oxygen plasma (selective oxidation). Step).

  Next, the wafer W ′ is unloaded from the chamber of the first process module 25 and loaded into the chamber 38 of the second process module 34 via the loader module 13. At this time, the wafer W ′ is mounted on the mounting table 39.

Next, the conditions in the chamber 38 are set to be the same as the conditions in the first embodiment. Then, HF gas is supplied from the gas supply unit 43 of the shower head 40 toward the wafer W ′ at a flow rate of 40 to 60 SCCM (HF gas supply step) (FIG. 4D). At this time, as in the first embodiment, the water molecules are substantially removed from the chamber 38 and the H ₂ O gas is not supplied into the chamber 38.

  Here, the HF gas that has reached the silicon monoxide film 64 is combined with water molecules contained in the silicon monoxide film 64 to become hydrofluoric acid. Then, this hydrofluoric acid removes the silicon monoxide film 64. On the other hand, even if the HF gas reaches the thermal oxide film 61 after the silicon monoxide film 64 is removed by hydrofluoric acid and the thermal oxide film 61 is exposed, the thermal oxide film 61 contains almost no water molecules. HF gas hardly becomes hydrofluoric acid, and the thermal oxide film 61 is hardly removed. Even if the nitrided portion 63a is exposed, the nitrided portion 63a is made of SiN, and SiN hardly reacts with hydrofluoric acid, so the nitrided portion 63a is hardly removed. As a result, the silicon monoxide film 64 is selectively etched and removed, and a nitride portion 63a is formed on the side surface of the gate electrode 62 (FIG. 4E). The nitriding portion 63a functions as a spacer that separates the gate electrode 62 from the source / drain in an LDD (Light Doped Drain) structure.

  Next, the wafer W ′ is unloaded from the chamber 38 of the second process module 34, and this process ends.

  According to the substrate processing method according to the present embodiment, the active species 53 in the oxygen plasma faces the silicon nitride film 63 covering the side surface and the top surface of the gate electrode 62 substantially parallel to the side surface (with respect to the surface of the wafer W ′). The active species 53 in the oxygen plasma comes into contact with the silicon nitride film 63. Since the thickness along the moving direction of the active species 53 in the silicon nitride film 63 covering the side surface of the gate electrode 62 (the direction perpendicular to the surface of the wafer W ′) is large, the active species 53 in the oxygen plasma is It is not possible to fully enter the part that covers the side. As a result, the flat portion covering the top surface of the gate electrode 62 and the flat portion not covering the gate electrode 62 in the silicon nitride film 63 are changed to the silicon monoxide film 64 by the active species 53 in the oxygen plasma. On the side surface of the electrode 62, a nitride portion 63a that does not change in the silicon monoxide film 64 remains. The hydrofluoric acid generated from the HF gas selectively etches the silicon monoxide film 64 changed from the silicon nitride film 63, but hardly etches the nitrided portion 63a. Therefore, in the silicon nitride film 63, other portions, specifically, a flat portion covering the top surface of the gate electrode 62 and the gate electrode 62 are removed without removing the nitride portion 63a covering the side surface of the gate electrode 62. The flat portion of the silicon nitride film 63 that is not covered can be selectively removed.

  In the substrate processing method described above, it is difficult to completely remove all silicon monoxide with hydrofluoric acid. Needless to say, the nitride portion 63a and the like contain some silicon monoxide.

  In each of the above-described embodiments, the silicon nitride film is oxidized using oxygen plasma. However, what is used for oxidizing the silicon nitride film is not limited to this, and any plasma containing at least oxygen can be used.

  In each embodiment described above, when the oxygen plasma is brought into contact with the silicon nitride film 52 (silicon nitride film 53) of the wafer W, no bias voltage is applied to the lower electrode in the first process module 25. In order to bring the oxygen plasma into contact with the silicon nitride film 52 with certainty, a bias voltage may be applied to the lower electrode.

  In addition, the substrate to which the substrate processing method according to each embodiment is applied is not limited to a wafer for a semiconductor device, and various substrates used for LCDs, FPDs (Flat Panel Displays), photomasks, CD substrates, printed boards, etc. It may be.

  An object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and store the computer (or CPU, MPU, etc.) of the system or apparatus. It is also achieved by reading and executing the program code stored on the medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention. .

  Examples of the storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, and a DVD. An optical disc such as RW or DVD + RW, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used. Alternatively, the program code may be downloaded via a network.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code. Includes a case where the functions of the above-described embodiments are realized by performing part or all of the actual processing.

  Furthermore, after the program code read from the storage medium is written to a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the expanded function is based on the instruction of the program code. This includes a case where a CPU or the like provided on the expansion board or the expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

It is a top view which shows schematic structure of the substrate processing system which performs the substrate processing method which concerns on the 1st Embodiment of this invention. FIG. 2 is a cross-sectional view of a second process module in FIG. 1, FIG. 2A is a cross-sectional view taken along line I-I in FIG. 1, and FIG. 2B is an enlarged view of portion A in FIG. FIG. It is process drawing which shows the substrate processing method which concerns on the 1st Embodiment of this invention. It is process drawing which shows the substrate processing method which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate processing system 11 1st process ship 12 2nd process ship 25 1st process module 34 2nd process module 38 Chamber 39 Mounting stand 40 Shower head 43 Gas supply part 50, 60 Silicon substrate 51, 61 Heat Oxide films 52, 63 Silicon nitride film 53 Active species 54, 64 Silicon monoxide film 62 Gate electrode

Claims (7)

A substrate processing method for processing a substrate having a thermal oxide film and a nitride film formed by a thermal oxidation process,
An oxygen plasma contact step for contacting the substrate with oxygen-containing plasma;
And a HF gas supply step of supplying HF gas toward the substrate in contact with the plasma containing oxygen. The substrate includes a convex conductive portion protruding on the thermal oxide film, and the nitride film covers a side surface and a top surface of the conductive portion,
2. The substrate processing method according to claim 1, wherein in the oxygen plasma contact step, active species in the oxygen-containing plasma move substantially parallel to the side surface and contact the nitride film.   The substrate processing method according to claim 2, wherein the active species includes at least a cation.   4. The substrate processing method according to claim 2, further comprising a selective oxidation step of selectively oxidizing the flat portion of the nitride film. The substrate includes a convex conductive portion projecting vertically from the surface of the substrate on the thermal oxide film, and the nitride film covers a side surface and a top surface of the conductive portion,
2. The substrate processing method according to claim 1, wherein in the oxygen plasma contact step, active species in the plasma containing oxygen move substantially perpendicular to the surface of the substrate and contact the nitride film.   6. The substrate processing method according to claim 5, further comprising a selective oxidation step of selectively oxidizing the flat portion of the nitride film. In a substrate processing apparatus for processing a substrate having a thermal oxide film and a nitride film formed by a thermal oxidation process,
An oxygen plasma contact device for contacting the substrate with oxygen-containing plasma;
A substrate processing apparatus comprising: an HF gas supply device that supplies HF gas toward the substrate in contact with the oxygen-containing plasma.

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