JP4124800B2 - Surface treatment method and apparatus - Google Patents

Description

  The present invention relates to a surface treatment method for removing an oxide film formed on the surface of an object to be processed, such as a semiconductor wafer, attached contaminants, etc., in particular a natural oxide film or attached oxide, and a surface treatment apparatus used therefor.

  In general, in a manufacturing process of a semiconductor integrated circuit (hereinafter referred to as a semiconductor element), a predetermined film forming process and a pattern etching process are repeatedly performed on a substrate such as a semiconductor wafer which is an object to be processed. A large number of semiconductor elements are formed.

  As described above, when a predetermined process is performed on an object to be processed, the object to be processed (eg, a semiconductor wafer (hereinafter referred to as “wafer”)) needs to be transported between the processing apparatuses. . For this reason, it has been practically difficult to avoid exposing the wafer to the atmosphere. When the wafer is exposed to the atmosphere, the surface of the wafer reacts with oxygen and moisture in the atmosphere, and as a result, a so-called natural oxide film is easily generated on the surface. Further, during various processes, there is a possibility that contaminants such as so-called chemical oxides may adhere to the surface of the wafer due to the atmosphere, a processing gas, a processing solution, or the like.

  Such a natural oxide film and contaminants cause deterioration of characteristics of the semiconductor element, for example, electrical characteristics. In order to avoid this cause, a surface treatment for removing a natural oxide film or the like on the wafer surface is performed as a pretreatment such as a film formation treatment on the wafer.

  Conventionally, as the surface treatment for removing a natural oxide film or the like, so-called wet cleaning in which a wafer is immersed in a chemical solution to remove the natural oxide film or the like on the surface of the wafer has been generally employed. As the integration of semiconductor elements increases, the element size, for example, the line width, contact hole diameter, or via hole diameter becomes finer. For example, the aspect ratio of the contact hole is increasing, and the diameter is about 0.2 to 0.3 μm or less (for example, 0.12 μm). Due to this fine element structure, in the above wet cleaning, the chemical solution does not sufficiently penetrate into such a fine contact hole, or the chemical solution that has entered the contact hole is removed from the contact hole due to its surface tension. There was a situation where it was not discharged. Therefore, serious problems such as a natural oxide film formed at the bottom of the contact hole cannot be sufficiently removed and a watermark is generated.

  In addition, when an object to be processed having a laminated structure composed of a plurality of layers is subjected to wet cleaning, the etching rate of each layer constituting the wall surface of the contact hole is different, which causes problems such as unevenness on the wall surface of the hole. .

FIGS. 10A and 10B show contact holes 302 formed in a stacked structure on the wafer W for making electrical contact with drains and sources. The hole diameter D shown in FIG. 10A is about 0.2 to 0.3 μm. As shown in FIG. 10A, the wall surface of the hole 302 has a multilayer structure made of a silicon oxide film (SiO ₂ ) formed by a plurality of film forming processes, for example, a three-layer structure. In this three-layer structure, for example, the first-layer SiO ₂ film 304 is a film formed by thermal oxidation, and the second-layer SiO ₂ film 306 is phosphorus-doped glass formed by spin coating. The third-layer SiO ₂ film 308 is a film formed of silica glass. As shown in FIG. 10A, the natural oxide film 310 is generated at the bottom of the contact hole 302.

  In such a multi-layered film formation layer, the etching rate of each layer with respect to the chemical solution for wet cleaning is different. After performing wet cleaning to remove the natural oxide film 310, as shown in FIG. 10B, the unevenness 309 due to the above-described difference in etching rate occurs on the sidewall of the hole 302, Alternatively, the conventional wet cleaning has a problem that the boundary portion is etched excessively (see the cut portion) because the chemical solution easily enters the boundary portion between the layers.

  Therefore, in order to solve such problems in the conventional wet cleaning, a method of removing a natural oxide film on an object to be processed using an etching gas, a so-called dry cleaning (etching) method has been proposed (for example, JP-A-5-275392, JP-A-6-338478, JP-A-9-106977).

FIG. 11 shows a conventional method for dry etching a SiO ₂ film as disclosed in Japanese Patent Laid-Open No. 5-275392. A dry cleaning method that uses this dry etching method to remove a natural oxide film on an object to be processed will be described. In the dry etching apparatus of FIG. 11, the on-off valve 450 is closed, and the Ar gas from the Ar gas source 454 is kept shut off. Close valve 436, 438 is opened, the NF ₃ gas source 444 and the H ₂ gas source 446 Prefecture, via a flow rate adjustment by the flow controller (MFC) 440, 442, to NF ₃ gas and H ₂ gas pipe 432 It is sent. In the pipe 432, both gases become, for example, a mixed gas having an NF ₃ / H ₂ mixing ratio of 1: 2 and a total pressure of 26.6 Pa (0.2 Torr). A microwave having a frequency of 2.45 GHz and a power of 50 W is supplied from the magnetron through the microwave wave tube 448, and the mixed gas is converted into plasma in the pipe 432. Fluorine activated species F ^* , hydrogen activated species H ^* , and nitrogen activated species N ^* generated in this plasmaization move toward the chamber 410 in the pipe 432 and enter the buffer chamber 430 in the chamber 410. Through the perforated plate 428, the wafer W is supplied on the wafer W placed on the susceptor 412 downstream. The wafer W is cooled by a cooling medium cooled to a room temperature or lower supplied from the cooling medium supply device 418 to the susceptor 412. The activated species F ^* , H ^* , and N ^* activated by the plasma descend onto the cooled wafer W, are adsorbed by the natural oxide film on the surface of the wafer W, and react with SiO ₂ . The product resulting from this reaction is vaporized and sucked into the vacuum pump 466 from the exhaust port 460 provided at the bottom of the chamber 410 and exhausted out of the system.

A method of removing a natural oxide film on a cooled wafer surface with fluorine active species F ^* , hydrogen active species H ^* , and nitrogen active species N ^* generated by such conventional plasma (Japanese Patent Laid-Open No. 5-275392) ), NF ₃ is decomposed by being turned into plasma, and as a result, F ^* and N ^* are formed. Therefore, the active gas of NF ₃ cannot be formed efficiently. Further, since H ₂ gas has a characteristic that it is difficult to maintain a plasma state in a single state, it is not always possible to obtain an etching rate sufficient for removing the natural oxide film.

Further, other methods of removing the natural oxide film by dry cleaning (JP-A-6-338478, JP-A-9-106977) all use H ₂ gas alone, so the natural oxide film is sufficiently removed. It was difficult to secure an etching rate necessary for the purpose.

An object of the surface treatment method and apparatus of the present invention is to solve the problems of such a conventional method for removing an oxide film such as a natural oxide film. In the present invention, in order to remove an oxide film having a thickness of about 10 to 20 angstroms from the surface of the object to be processed, H ₂ gas and N ₂ gas are used as plasma gases, and the activity of these mixed gases converted into plasma is activated. NF ₃ gas (reactive gas) is added during the seed flow. The object to be processed is cooled to room temperature or lower, and the oxide film on the object to be processed reacts with the reaction gas to form a reaction film. Thereafter, the object to be processed is heated to a predetermined temperature or higher, and the reaction film formed on the surface of the object to be processed is removed.

In the present invention, a process of carrying an object having an oxide film on the surface thereof into the processing container, a process of evacuating the processing container, and a gas containing N and H are introduced into the plasma generator. And forming the respective active gas species by plasmaizing and activating the gas, causing the active gas species to flow toward the object to be processed, and NF to the flowing active gas species. by adding ₃ gas, said forming a NF ₃ gas activated gas, cooling the該被processed below a predetermined temperature, the activated gas in the NF ₃ gas There is provided a surface treatment method comprising the step of altering the oxide by reacting with the oxide on the surface of an object to be treated.

In this surface treatment method, the gas containing N and H is a mixed gas of N ₂ gas and H ₂ gas. Following the step of altering the oxide, the N ₂ gas, H ₂ gas, and the gas The process of sublimating the reaction film by stopping the supply of NF ₃ gas to the processing vessel and heating the object to be processed to a predetermined temperature, the vacuum evacuation, and the oxide film were removed. And a step of unloading the object to be processed from the processing container.

  In this surface treatment method, the predetermined temperature for cooling the object to be treated is set to room temperature or lower.

  In this surface treatment method, the predetermined temperature for cooling the object to be treated is in the range of 20 ° C. to −20 ° C.

  In this surface treatment method, the predetermined temperature for cooling the object to be treated is in the range of 10 ° C. to −20 ° C.

  In this surface treatment method, the predetermined heating temperature for sublimating the reaction film is set to 100 ° C. or higher.

  Further, in the present invention, a plasma generating unit that converts the plasma forming gas into plasma, a processing vessel that is connected to the plasma generating unit and has a mounting table on which the object to be processed is mounted, and the mounting table Means for cooling the mounted object to be processed to a predetermined temperature, elevating means for raising the object to be heated in the processing container to a heating position, and heating the object to be processed to a predetermined temperature at the heating position There is provided a surface treatment apparatus having heating means.

  The surface treatment apparatus is an apparatus for removing a natural oxide film formed on the surface of the object to be treated.

In addition, the surface treatment apparatus is activated by the plasma generation gas introduction unit that supplies N ₂ gas and H ₂ gas as plasma formation gas to the plasma generation unit, and is activated by the plasma generation unit. the N ₂ gas and an active gas species of the H ₂ gas that flows toward, further comprising a NF ₃ gas supply section for adding the NF ₃ gas, and wherein the addition of the NF ₃ gas, NF ₃ A gas activated gas is formed, and the activated gas of the NF ₃ gas is reacted with the surface layer on the object to be processed to alter the surface layer.

  Moreover, in this surface treatment apparatus, the predetermined temperature which cools the to-be-processed object mounted in this mounting base is below normal temperature.

  In this surface treatment apparatus, the predetermined temperature for cooling the object to be treated placed on the placing table is in the range of 20 ° C to -20 ° C.

  In this surface treatment apparatus, the predetermined temperature for cooling the object to be treated placed on the placing table is in the range of 10 ° C. to −20 ° C.

  In this surface treatment apparatus, the predetermined temperature for heating the object to be treated at the heating position is a temperature of 100 ° C. or higher.

Further, in this surface treatment apparatus, the NF ₃ gas supply unit includes a large number of gas ejection holes provided on the inner wall of the treatment container.

Further, in this surface treatment apparatus, the NF ₃ gas supply unit includes, for example, a ring-shaped or lattice-shaped shower head having a large number of gas ejection holes provided in the processing container.

Further, in this surface treatment apparatus, the NF ₃ gas supply unit adds the NF ₃ gas to the active gas species at a position at least 20 cm away from the end of the plasma generation unit in the direction of the object to be processed.

  Moreover, in this surface treatment apparatus, the heating means is a heat radiation means provided above the object to be treated.

  In this surface treatment apparatus, the heating means is a heating lamp provided above the object to be treated.

  Furthermore, in the present invention, the object to be processed is transferred to the surface treatment apparatus through the transfer chamber in one or more metal wiring forming chambers, heating chambers, and load lock chambers in a non-reactive atmosphere. Thus, the provided cluster device is provided.

  In this cluster apparatus, one or a plurality of metal wiring forming chambers, a heating chamber, a cooling chamber, and a load lock chamber are provided via a transfer chamber so that the object to be processed is transferred in a non-reactive atmosphere.

  In this cluster apparatus, the metal wiring forming chamber is a chamber for forming at least one film of Al, Ti, TiN, Si, W, WN, Cu, Ta, TaN, and SiN.

  Further, in this cluster apparatus, the metal wiring forming chamber includes means for heating the object to be processed to a temperature of at least 100 ° C. or higher.

As described above, according to the surface treatment method and apparatus of the present invention, a gas containing N and H is activated by plasma formation to form an active gas species, and a reactive gas (NF ₃ gas) is formed by the active gas species. ), While cooling the object to be treated at room temperature or lower, these three gases react with the oxide film generated on the surface of the object to be modified to form a reaction film. By sublimating, an oxide film on the surface of the object to be processed, for example, a natural oxide film, can be removed extremely efficiently and at a high etching rate.

In this embodiment, N ₂ gas and H ₂ gas are used as the gas containing N and H, but other gas such as ammonia can be used as the gas containing N and H. .

  Further, the ring-shaped and lattice-shaped structures have been described as the shower head for ejecting the activated gas of the present invention, but any other structure can be adopted as the shower head.

  Furthermore, since the surface treatment apparatus of the present invention and the other treatment apparatus are clustered in a non-reactive atmosphere, for example, in vacuum, so that the objects to be processed can be conveyed in a vacuum, there is no generation of an oxide film during the transfer, As a result, throughput is improved.

  Embodiments of a surface treatment method and a surface treatment apparatus according to the present invention will be described below with reference to the accompanying drawings.

  First, an embodiment of a surface treatment (oxide removal) apparatus will be described.

FIG. 1 is a conceptual configuration diagram of a surface treatment apparatus of the present invention. The surface treatment apparatus is a contaminant (eg, natural oxide film, or intention) generated on the surface of an object to be treated (eg, a semiconductor wafer) (hereinafter referred to as “wafer W”) having a thickness of 10 to 20 angstroms or less. Without being carried out, it can be used to remove chemical oxides that are naturally attached to or formed on the surface (hereinafter referred to as “natural oxide film”). The surface treatment apparatus 1 shown in FIG. 1 converts a mixed gas of N ₂ gas and H ₂ gas into plasma, removes a plasma forming tube 30 that activates the gas, and a natural oxide film generated on the surface of the wafer W. For this purpose, a processing vessel 10 and a reaction gas supply pipe 26 for supplying NF ₃ gas (reaction gas) from the NF ₃ gas source into the processing vessel 10 are provided.

The processing vessel 10 can be made of an aluminum material, and the inner wall thereof can be protected from metal contamination, erosion, and the like by being provided with linings 13 and 14 made of quartz (SiO ₂ ). The processing container 10 may be a cylindrical housing body, and the cross section thereof may be various shapes such as a circle, a rectangle, and a polygon. A bottom plate 12 having a predetermined thickness is fixed to the bottom of the processing container 10. A base 29 can be disposed on the bottom plate 12. A cylindrical wafer mounting table (susceptor) 20 can be provided on the base 29. The wafer W is mounted on the upper surface of the wafer mounting table 20 and can be locked by a quartz clamp ring 21. Inside the cylindrical mounting table 20, a jacket (or pipe) 22 for storing a cooling medium (chiller) and a heat exchanger 23 are provided. The jacket (or pipe) 22 may be provided integrally with the heat exchanger 23. The cooling medium is supplied from the cooling medium supply device 42 into the jacket (or pipe) 22 through the cooling pipe 43, and the wafer W is cooled to a predetermined temperature, for example, normal temperature or lower.

The mounting table 20 can be provided with wafer lift means, as will be described later. This wafer lift means is a mechanism that raises the wafer W from the mounting table 20 to a predetermined heating position (L ₂ ) when heating the wafer W, and lowers the wafer W again to return it to the mounting table after predetermined processing. Yes, a pin driving mechanism 25, a support pin 24a, and an arm 24 can be provided. An example of this wafer lift means is shown in FIGS. 2 (a) and 2 (b). A hydraulic cylinder 25 (pin drive mechanism) is disposed on the lower surface of the base 29 provided at the lower portion of the processing container 10, and a horseshoe-shaped support piece 24b is fixed to the tip of the cylinder rod 25a. Support pins 24a are fixed to predetermined positions (for example, three positions) of the arm 24 extending radially inward from the support piece 24b. The support pins 24a can have a pointed head at the tip protruding upward, and the wafer W is horizontally supported at three points by the pointed head. When the wafer is heated by the heat radiation means (eg, heating lamp) 19, the wafer W is raised (UP) to the heating position (L ₂ ) shown in FIG. 1 by the wafer lift means.

  Exhaust pipes (for example, four exhaust pipes) 40 can be provided on the peripheral edge of the bottom plate 12 fixed to the bottom of the processing container 10. The inside of the processing vessel 10 is evacuated by an evacuation unit (for example, a vacuum pump) 41 connected to the exhaust pipe 40.

  A top plate 11 (eg, made of aluminum material) can be fixed to the upper portion of the processing container 10. The top plate 11 may be provided with a quartz cover (dome) 15 having a flange portion 16 via a seal member (eg, rubber O-ring) 17. The cover 15 can be formed integrally with the quartz plasma forming tube 30, and the shape thereof can be various shapes such as a flat shape as well as a dome shape. A monitoring device such as a pressure sensor can be disposed on the seal portion provided with the seal member 17. These monitoring devices monitor the tightening pressure of the seal portion, the presence or absence of gas leakage from the seal portion, and the like.

  A number of heating lamps 19 can be provided above the cover 15 as heat radiation means for heating the wafer W from above. The heating lamp 19 can be a halogen lamp so that the wafer W can be rapidly heated. The heat rays emitted from the heating lamps 19 pass through the transparent quartz dome 15 and enter the surface of the wafer W raised to the heating position, and the wafer W is heated to a temperature of 100 ° C. or higher (eg, 120 ° C).

  By covering the heating lamp 19 with a cover 18 made of metal or the like, it is possible to block heat rays and light rays radiated from the heating lamp 19 to the outside, and even if the quartz dome 15 is damaged, plasma gas or Reaction gas can be prevented from diffusing or leaking outside.

  A gate valve 10 a that communicates with a transfer chamber, a load lock chamber, and the like is provided on the side wall of the processing container 10. The gate valve 10a is opened and closed when the wafer W is loaded and unloaded.

Here, since the NF ₃ gas hardly etches the metal surface, it is usually not necessary to protect the inner surface of the gate valve 10a with quartz. In general, the metal inner surface of the processing vessel is coated with quartz in order to prevent the life of the activated species whose metal surface is activated by plasma from being shortened. In this sense, the inner surface of the gate valve 10a is preferably covered with quartz.

  A quartz plasma forming tube 30 for forming a plasma gas can be integrally provided at the upper center of the quartz cover 15 by fusion bonding or the like, and the plasma forming tube 30 is processed at the center of the cover 15. Opening into the container 10, plasma is introduced into the processing container 10 through the opening. Any configuration that allows uniform surface treatment for the formation and introduction of plasma gas can be employed. For example, a configuration in which plasma is introduced from a position shifted from the center of the cover 15 or a configuration in which plasma is introduced from the side of the processing vessel 10 can be employed.

A plasma forming gas introducing portion 33 is connected to the upper end portion of the plasma forming tube 30. From N ₂ gas source 35 and H ₂ gas source 36, through the flow controller (MFC) 344, N ₂ gas and H ₂ gas is supplied to the gas passage 33a. These mixed gases (N ₂ + H ₂ ) are supplied to the plasma generation part of the plasma forming tube 30 inside the plasma cavity 31 through the introduction part 33.

A microwave generation source 32 can be connected to the plasma cavity 31. Microwaves generated by the microwave generation source 32 (for example, 2.45 GHz microwaves) are applied to the plasma cavity 31 to excite the plasma forming gas in the plasma forming tube 30, and the N ₂ and H ₂ The mixed gas is activated to form active gas species of N ^* radicals and H ^* radicals. Those active gas species are supplied into the processing vessel 10 from the opening 30 a of the plasma forming tube 30.

A large number of gas ejection holes 26 a for supplying NF ₃ gas are provided at a position L ₁ below the opening 30 a of the plasma forming tube 30. This position L ₁ is preferably at least 20 cm or more, more preferably 30 cm or more from the lower end of the plasma cavity 31 of the plasma forming tube 30 (plasma generating part). An NF ₃ gas source 28, a flow rate controller (MFC) 27, a conducting pipe 26, a pipe 26b provided around the outer wall of the processing vessel 10, and a conducting pipe 26c provided through the wall of the processing vessel 10 The NF ₃ gas having a predetermined flow rate can be supplied to the gas ejection holes 26a via the.

  In FIG. 1, the gas ejection hole 26 a is shown as a structure slightly projecting inward from the inner wall surface of the processing container 10. However, the gas supply hole 26a and the gas supply structure extending from the conduction pipe 26 to the gas discharge hole 26a are not limited to the structure shown in FIG.

  FIG. 8 illustrates another embodiment of the gas supply structure. In FIG. 8, a pipe 26b and a conducting pipe 26c are provided inside the wall of the processing vessel 10 which can be manufactured from aluminum. The pipe 26 b and the conductive pipe 26 c can be integrated with the wall inside the processing vessel 10. In FIG. 8, the gas ejection hole 26 a is configured not to protrude from the inner wall surface of the processing container 10. This structure allows the gas to be uniformly diffused into the processing vessel and does not disturb the flow of plasma gas from the upstream.

As an alternative structure of the gas ejection hole 26a shown in FIG. 1, a shower head 261b is shown in FIG. The shower head 261b has a ring shape and is made of quartz. The shower head 261b has a number of gas ejection holes 261a. These gas ejection holes 261a can be provided downward (in the direction of the mounting table 20), laterally, or obliquely on the circumference of the shower head 261b. The conducting tube 261 is connected to the ring-shaped shower head 261a. The shower head 261 a is horizontally disposed at a predetermined position in the processing container 10, and NF ₃ gas is supplied into the processing container 10.

  FIG. 3B shows a lattice-shaped shower head 262b having a large number of gas ejection holes 262a. Also in the lattice-like shower head 262b, the gas ejection holes 262a can be provided downward, laterally, or obliquely.

  Furthermore, means (not shown) for adjusting the flow of plasma gas can be provided in the opening 30 a of the plasma forming tube 30. This adjusting means can be a cylindrical or umbrella-shaped cover that opens from the opening 30 a toward the mounting table 20.

  Next, the surface treatment (natural oxide film removal) method of the present invention will be described.

  In the surface treatment (natural oxide film removal) apparatus configured as described above, the surface treatment (natural oxide film removal) method of the present invention will be described based on the flowchart of FIG.

  Step (a): The gate valve 10a of the surface treatment apparatus 1 shown in FIG. 1 is opened, and one wafer W passes through the gate valve 10a from the transfer chamber and is in a non-reactive atmosphere (eg, in vacuum). Then, it is carried into the processing container 10, placed on the mounting table (susceptor) 20, and locked to the mounting table 20 by the clamp ring 21. On the wafer W, a contact hole 302 (see FIG. 10A) or the like is formed in the previous process, and an oxide (as shown in FIG. 5A) is formed on the wafer W on the surface of the bottom of the hole. For example, a natural oxide film) 80 is formed.

  Step (b): After the wafer W is loaded into the processing container 10, the gate valve 10a is closed, the processing container 10 is evacuated by the vacuum pump 41 via the exhaust pipe 40, and the processing container 10 is evacuated. The atmosphere becomes (eg, 0.133 Pa or less (1 mTorr or less)).

  Step (c): By cooling with the cooling medium supplied from the cooling medium supply device 42 to the susceptor 20, the wafer W becomes room temperature or lower.

Step (d): N ₂ (nitrogen) gas and H ₂ (hydrogen) gas are controlled by a flow rate controller (MFC) 34 from the N gas source 35 and H gas source 36 and supplied to the gas passage 33a. The mixed gas (N ₂ + H ₂ ) is supplied as a plasma forming gas from the plasma gas introducing portion 33 into the plasma forming tube 30.

Step (e): Microwaves (2.54 GHz) from the microwave generation source 32 are introduced into cavities provided around the plasma generation part of the plasma forming tube 30. The mixed gas of N ₂ gas and H ₂ gas supplied to the plasma generator is turned into plasma by the microwave and activated, and N ^* radicals and H ^* radicals, which are active gas species, are formed. In particular, H ₂ gas which is not easily converted to plasma can be efficiently converted to plasma and activated with the help of N ₂ gas. These active gas species N ^* and H ^* are attracted to the vacuum atmosphere in the processing vessel 10 and flow from the plasma generation part in the plasma forming tube 30 toward the opening (outlet) 30a.

Step (f): The reactive gas NF ₃ is supplied from the NF ₃ gas source 28 provided outside the processing vessel 10 to the reactive gas supply pipe 26 via the flow rate controller (MFC) 27, and a number of gas jets are ejected. It is supplied in the shape of a shower into the processing container 10 from the hole 26a. The supplied NF ₃ gas is added to the active gas species N ^* and H ^* radicals formed by converting the N gas and H gas flowing from the opening 30a of the plasma forming tube 30 into plasma. As a result, the added NF ₃ gas is activated by the flowing active gas species N ^* and H ^* .

Step (g): The natural oxide film 80 of the wafer W shown in FIG. 5 (a) is altered by the synergistic action of the NF ₃ gas and the flowing active gas species N ^* and H ^* . Then, as shown in FIG. 5B, a reaction film 82 in which Si, N, H, F, and O are mixed is formed. In the stage of changing to the natural oxide film 80, a cooling medium (for example, ethylene glycol) by the cooling medium supply device 42 shown in FIG. 1 is supplied into the mounting table 20, and the wafer W on the mounting table 20 is kept at room temperature or lower. It is cooled.

This cooling increases the etching rate with the NF ₃ active gas. The process conditions at this time are as follows: gas flow rates of H ₂ , NF ₃ , and N ₂ are 10 sccm, 30 sccm, and 100 sccm, the process pressure is 399 Pa (3 Torr), the plasma power is 50 W, and the process time is about 3 minutes. preferable.

Since the etching rate of the etching species formed by the reaction between the NF ₃ gas and the H ₂ plasma gas is slow, these gases are adsorbed on the reaction surface and the reaction rate is determined. By cooling the wafer to a low temperature below room temperature, the adsorption rate is increased and the reaction rate can be increased.

As described above, the process of altering the natural oxide film 80 on the wafer W due to the synergistic action of the NF ₃ gas and the active gas species N ^* and H ^* may be performed at a temperature below room temperature. preferable.

FIG. 9 shows the relationship between the cooling temperature and the reaction rate in this step. In FIG. 9, the vertical axis represents the etching rate (speed), and the horizontal axis represents the cooling temperature of the wafer W at the start of the process. From FIG. 9, since the etching control characteristics become unstable when the cooling temperature exceeds 20 ° C., it is preferably below room temperature, more preferably in the range of 20 ° C. to −20 ° C., and further 10 ° C. A range of C to -20 ° C is suggested to be preferred. The experimental conditions for obtaining the data shown in FIG. 9 are as follows. Step of altering the natural oxide film 80: H ₂ / NF ₃ / N ₂ ratio ... 300/60/400 sccm, pressure ... 532 Pa (4 Torr), power ... 300 W, treatment time ... 1 minute (Sublimation process) Temperature ... 140 ° C, Sublimation process time ... 1 minute, Sublimation process atmosphere ... Vacuum.

Step (h): After altering the oxide film, the supply of H ₂ , N ₂ , NF ₃ gas is stopped, the driving of the microwave generation source 32 is stopped, and the introduction of the microwave into the plasma forming tube 30 is also performed. Stopped. The inside of the processing container 10 is further evacuated from the exhaust pipe 40.

  Step (i): The wafer lift means is driven, and the wafer W is raised to a heating position at least 5 mm away from the wafer mounting table 20.

  Step (j): The heating lamp 19 is turned on, the wafer W is heated from above, and its surface is rapidly heated from room temperature to a temperature of 100 ° C. or higher (eg, about 120 ° C.).

  Step (k): The reaction film 82 in which Si, N, H, F, and O are mixed by heating with the heating lamp 19 is made of Si, N, H, F, and O, as shown in FIG. The mixed gas 84 is sublimated, removed, and exhausted from the exhaust pipe 40. By this sublimation, the natural oxide film 80 (reaction film 82) is removed from the wafer W, and an Si surface appears on the surface of the wafer W. The process conditions at this time are preferably a process pressure of 0.133 Pa (1 mTorr or less) and a process time of about 2 minutes.

  Step (l): The heating lamp 19 is turned off.

  Step (m): Finally, evacuation is stopped.

  Step (n): The gate valve 10a is opened and the wafer lift means is driven to lower the wafer W and return it to the wafer mounting table 20. The wafer W from which the natural oxide film has been removed is unloaded from the processing container 10 and is transferred to an adjacent chamber (eg, transfer chamber) in a vacuum atmosphere.

The oxide film to be subjected to the surface treatment method of the present invention is an extremely thin (about 10 to 20 angstrom) oxide film grown on W, Ti, Al, Ni, Co and their silicides in addition to SiO _2. Is also included.

  The surface treatment apparatus of the present invention can be combined with other treatment apparatuses (eg, metal wiring formation chamber, heating chamber, cooling chamber, transfer chamber, and load lock chamber) to constitute a multi-chamber type cluster apparatus. it can.

  Hereinafter, the configuration of the cluster apparatus will be described.

  The vacuum cluster apparatus 100 shown in FIG. 6 is an apparatus 100 that can transfer a wafer in a non-reactive atmosphere (eg, a vacuum atmosphere). In this vacuum cluster apparatus 100, the surface treatment (natural oxide film removal) apparatus of the present invention is a natural oxide film removal chamber 101, and a heating chamber 102, one or a plurality of metal wirings via a transfer chamber 105. A forming chamber 103 and a load lock chamber 104 are disposed. The metal wiring formation chamber 103 forms metal wiring of Al, Ti, TiN, Si, W, WN, Cu, Ta, and SiN on the object to be processed by metal CVD. A gate valve 107 is provided between the chambers, and a transfer robot 106 is provided in the transfer chamber 105.

  The wafer cassette containing the wafer is transferred into the load lock chamber 104, and the wafer is aligned in the transfer chamber 105 with reference to the orientation flat. The gate valve 107 is opened, and the wafers are carried one by one into the natural oxide film removal chamber 101 by the transfer robot 106. After the oxide film on the surface of the wafer is removed, the wafer is heated in advance in the heating chamber 102. Alternatively, in a plurality of metal wiring forming chambers 103, metal wirings such as Al and Ti are formed in the contact holes of the wafer by metal CVD or the like, and finally the wafer W is carried out to the load lock chamber 104.

  Another vacuum cluster apparatus 200 shown in FIG. 7 can transfer a wafer in the same non-reactive atmosphere. The natural oxide film removal chamber 201 of the present invention includes a heating chamber 202, one or a plurality of metal wiring forming chambers 203, a cooling chamber 204, and a load lock chamber 205 via a transfer chamber 206. A gate valve 208 is provided between the chambers, and a transfer robot 207 is provided in the transfer chamber 206.

  When a wafer after wiring formation is transferred to the load lock chamber 205 from a metal wiring formation chamber 203 that is normally heated to a temperature of about 500 ° C., the temperature of the wafer (about about the temperature that the load lock chamber 205 can accept) 150 ° C.). For this reason, the vacuum cluster apparatus 200 is provided with a cooling chamber 204 in particular.

  In the vacuum cluster apparatus shown in FIGS. 6 and 7, when the heating chambers 102 and 202 include means for heating to a temperature of 100 ° C. or higher, the heating means for the natural oxide film removal chambers 101 and 201 is used. Can be omitted.

  By configuring the vacuum cluster device as described above, it is possible to prevent the natural oxide film from being regenerated by transporting the wafer in the atmosphere. Time management from the removal of the natural oxide film to the film formation becomes unnecessary, and the generation of water marks can be prevented. The effects of being able to remove the natural oxide film on the wafer in situ, greatly improving the throughput, and the like are exhibited.

It is a schematic block diagram of one embodiment of the surface treatment apparatus of the present invention. 2A and 2B show an example of a wafer lift mechanism that can be used in the surface treatment apparatus shown in FIG. 1, FIG. 2A is a plan view thereof, and FIG. ) Is a side view thereof. 3A and 3B show an alternative example of the NF ₃ gas supply unit (shower head) that can be used in the surface treatment apparatus shown in FIG. 1, and FIG. FIG. 3B is a plan view of the lattice-shaped shower head as viewed from the wafer mounting table side. It is a flowchart which shows each process of embodiment concerning the surface treatment method of this invention. 5 (a), 5 (b) and 5 (c) are diagrams showing a process of removing an oxide, for example, a natural oxide film, by the surface treatment method of the present invention. FIG. 5A is an enlarged view of a natural oxide film attached to the wafer, FIG. 5B is an enlarged view of a reaction film formed on the surface of the wafer, and FIG. The enlarged schematic diagram of the state which sublimates and removes the gas in which Si, N, H, F, and O were mixed from the reaction film by heating. FIG. 2 is a conceptual diagram of a vacuum cluster apparatus configured by using the surface treatment apparatus of the present invention shown in FIG. 1 as a natural oxide film removing apparatus in combination with a heating apparatus and a wiring forming apparatus. FIG. 2 is a conceptual diagram of a vacuum cluster apparatus configured by using the surface treatment apparatus of the present invention shown in FIG. 1 as a natural oxide film removing apparatus in combination with a heating apparatus, a wiring forming apparatus, and a cooling apparatus. Alternatives of NF ₃ gas supply section which can be used in the surface treatment apparatus of the present invention is a conceptual diagram showing a. It is a figure which shows the relationship between the temperature which cools a wafer, and the etching rate in the surface treatment apparatus of this invention. 10A and 10B are views for explaining a conventional surface treatment method for removing a natural oxide film. FIG. 10A shows a natural oxidation generated at the bottom of a contact hole of a wafer. FIG. 10B is an enlarged schematic view showing a state in which irregularities and the like are formed on the side wall of the contact hole due to the difference in the etching rate. The conventional NF ₃ gas, by etching with neutral gas species H ₂ gas is mixed, is a schematic view of an etching apparatus used in the method of removing the natural oxide film.

Explanation of symbols

1 Surface treatment equipment (natural oxide film removal equipment)
10 processing vessel 13 of quartz lining 15 quartz dome 18 heating unit cover 19 heat lamps 20 wafer mounting table 21 clamp ring 24 wafer lift means 25 pin drive mechanism 26 reaction gas (NF ₃₎ base plate supply pipe 28 NF ₃ gas source 29 30 plasma formation Tube (plasma generator)
31 Plasma cavity 32 Microwave generation source 33 Plasma gas introduction part 35 N ₂ gas source 36 H ₂ gas source 40 Exhaust pipe 41 Vacuum pump 100 Vacuum cluster device 101 Natural oxide film removal chamber 102 Heating chamber 103 Wiring formation chamber 104 Load lock chamber 105 transfer chamber 106 transfer robot 107 gate valve 200 vacuum cluster apparatus 201 natural oxide film removal chamber 202 heating chamber 203 wiring formation chamber 204 cooling chamber 205 load lock chamber 206 transfer chamber 207 transfer robot 208 gate valve

Claims (4)

In the surface treatment method for treating an object having an oxide film on the surface,
Activating a gas containing N and H in the plasma generating unit to form an active gas species comprising N radicals and H radicals;
Lateral or oblique when the direction of the mounting table for mounting the NF ₃ wherein the gas to be processed in a downstream region apart from an end of the plasma generating part and lower with respect to the flow of gas flow toward the object to be processed forming an active gas species of NF ₃ gas by activating NF ₃ gas is added to the direction,
Due to the synergistic action of the active gas species of the NF ₃ gas and the active gas species comprising the N radical and the H radical, these are exposed to the surface of the object to be treated and reacted with the oxide film to form Si, N, H Forming a reaction film in which F, O and O are mixed ;
A surface treatment method comprising: Sublimating the reaction film by heating the object to be processed;
The surface treatment method according to claim 1, further comprising: In a surface treatment apparatus for treating an object having an oxide film on the surface,
A plasma generating unit that forms an active gas species composed of N radicals and H radicals by activating a gas containing N and H;
Lateral or oblique when the direction of the mounting table for mounting the NF ₃ wherein the gas to be processed in a downstream region apart from an end of the plasma generating part and lower with respect to the flow of gas flow toward the object to be processed An NF ₃ gas supply section to be added in the direction;
Comprising
Activated gas species consisting of the NF ₃ the N radicals and H radicals as the active gas species of NF ₃ gas formed by activating a gas by said added to the active gas species of N radicals and H radicals As a result of a synergistic action with these, they are exposed to the surface of the object to be treated and reacted with the oxide film to form a reaction film in which Si, N, H, F and O are mixed .
The surface treatment apparatus characterized by the above-mentioned. Heating means for sublimating the reaction film by heating the object to be processed;
The surface treatment apparatus according to claim 3, further comprising:

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