JP2007329245A - Processing method and processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing method and a processing apparatus for removing oxides formed on the front surface of a metal material at the temperature not giving any damage on a metal material of the base material, or an area near the metal material using the processing gas including vapor. <P>SOLUTION: An oxide film is removed by placing a processing gas including vapor and an auxiliary removing substance having higher capability for removing oxide film than the vapor in contact with an object to be processed including, at its front surface, a metal part where an oxide film is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a processing method and a processing apparatus for removing an oxide formed on a surface of a metal used for a semiconductor device, for example.

  Recently, in response to demands for higher speeds of semiconductor devices, finer wiring patterns, and higher integration, there has been a demand for lower capacitance between wirings, improved wiring conductivity, and improved electromigration resistance. As a corresponding technology, copper (Cu), which has higher conductivity than aluminum (Al) and tungsten (W) and has excellent electromigration resistance, is used as a wiring material, and a low dielectric constant film (Low-k) is used as an interlayer insulating film. Cu multilayer wiring technology using a film) has attracted attention.

  In the Cu multilayer wiring formation step, a metal is buried in the via hole in order to make a via contact with the lower Cu wiring. However, since Cu is easily oxidized, an oxide is easily formed on the surface thereof. Since a good contact cannot be obtained if the oxide remains on the surface, it is necessary to remove the Cu surface oxide layer and reduce the wiring resistance before forming the contact with Cu.

  As a technique for removing copper oxide, Patent Document 1 discloses a method using water vapor. With this technology, copper oxide is removed by water vapor using the standard cast energy of copper oxide smaller than that of water vapor, and carbon, fluorine, etc. adhering to the surface are simultaneously removed. Can do.

However, in the technique described in Patent Document 1, since it is necessary to heat the semiconductor wafer to be processed to a high temperature of 300 ° C. or higher, there is a risk of damaging the Cu wiring or the Low-k film.
JP 2001-271192 A

  The present invention has been made in view of such circumstances, and removes an oxide formed on the surface of a metal at a temperature that does not damage the underlying metal or its nearby portion by using a processing gas containing water vapor. It is an object of the present invention to provide a processing method and a processing apparatus that can be used.

  In order to solve the above problems, according to a first aspect of the present invention, a process gas containing water vapor and a removal auxiliary substance having a higher ability to remove oxide film than water vapor is coated with a metal portion having a metal portion on which an oxide film is formed. Provided is a processing method characterized by contacting the processing body and removing the oxide film.

  In the first aspect, as a typical example, the metal portion can be made of copper and the oxide film can be made of copper oxide. More specifically, the object to be processed can be a semiconductor wafer.

  Examples of the removal auxiliary substance include carbon. In this case, examples of the processing gas include a gas produced by exposing carbon as the removal auxiliary substance to water vapor. It is preferable that the water vapor to which such carbon is exposed is 800 ° C. or higher. Moreover, the said carbon can be exposed to water vapor | steam by bubbling water vapor | steam to the said carbon. Examples of the removal auxiliary substance contained in the processing gas include those containing alkene. In this case, the processing gas further contains diborane, hydrogen peroxide, and ammonia or amine, or Furthermore, what contains ozone can be used. Furthermore, as the removal auxiliary substance contained in the processing gas, one containing acetal, one containing epoxide, one containing alkoxide, or one containing alkyne can be used.

  In the second aspect of the present invention, a processing container containing a target object having a metal portion having an oxide film formed on the surface thereof, and removal assistance having a higher ability to remove oxide film than water vapor and water vapor in the processing container. A processing gas supply mechanism for supplying a processing gas containing a substance, and supplying the processing gas into the processing container to bring it into contact with an oxide film formed on the surface of the metal portion of the object to be processed A processing apparatus for removing an oxide film is provided.

  In the second aspect, an exhaust mechanism for exhausting the inside of the processing container may be further provided, and the oxide film may be removed while exhausting the inside of the processing container to form a reduced pressure atmosphere. In addition, the apparatus may further include a control unit that controls the supply of the processing gas by the processing gas supply unit so that the oxide film formed on the surface of the metal portion of the object to be processed is removed. Moreover, you may further have a heating mechanism which heats a to-be-processed object within the said processing container.

  According to the present invention, since the gas containing water vapor and the removal auxiliary substance having a higher ability to remove the oxide film than water vapor is brought into contact with the oxide formed on the metal surface, the removal by the water vapor and the removal by the removal auxiliary substance are performed. Due to the synergistic effect, the metal oxide can be removed at a lower temperature than in the case of water vapor alone.

Hereinafter, embodiments of the present invention will be described.
1A to 1F are process cross-sectional views illustrating a processing method according to the first embodiment of the present invention. First, a low dielectric constant film (Low-k film) 3 is formed on the Si substrate 1 as an interlayer insulating film, a hard mask film 6 is formed on the Low-k film 3, and then patterned by photolithography. The hard mask film 6 is etched using the resist film (not shown) as a mask to form a hard mask, and the low-k film 3 is etched using the resist film and the hard mask as an etching mask to form grooves. A barrier metal film 4 and a Cu film 5 are formed in the trench, and an etch stopper film 7, a low-k film 8 and a hard mask film 9 are sequentially formed on the barrier metal film 4, the Cu film 5 and the hard mask film 6. A semiconductor wafer (hereinafter simply referred to as a wafer) having the structure shown in FIG.

  Next, the hard mask film 9 is etched using a resist film (not shown) patterned by photolithography as a mask to form a hard mask, and the low-k film 8 and the etching are further performed using the resist film and the hard mask as an etching mask. The stopper film 7 is etched to form a via hole 10 as shown in FIG.

  When the via hole 10 is thus opened and exposed to an oxidizing atmosphere, Cu is easily oxidized, so that a surface oxide film 11 as shown in FIG. 1C is immediately formed on the Cu film 5. Is done. When an oxide film is formed in this way, good contact cannot be made. Therefore, before forming a contact with Cu, it is necessary to remove the surface oxide film 11 of the Cu film 5 and reduce the wiring resistance.

  Therefore, in the present embodiment, as shown in FIG. 1D, the surface oxide film 11 is removed by a processing gas comprising water vapor and a removal auxiliary substance as will be described in detail below, and (e) in FIG. ), The oxide film is not present.

  Thereafter, as shown in FIG. 1F, a barrier metal film 12 is formed in the via hole 10, and a Cu film 13 is buried as a buried metal to form a via contact.

Next, the removal process of the surface oxide film will be specifically described.
In this embodiment, a wafer in which the surface oxide film 11 is formed on the Cu film 5 as shown in FIG. 1C is applied to the oxide film rather than water vapor and water vapor as shown in FIG. By bringing a processing gas containing a removal auxiliary substance having a high removal ability into contact with the surface thereof, the surface oxide film 11 formed on the surface of the Cu film 5 is removed so that the surface oxide film does not exist.

  Here, the removal auxiliary substance contained in the processing gas is a substance that generates a substance having a higher removal ability for copper oxide than water vapor, even if the substance itself has a higher removal ability for copper oxide than water vapor. Also good. In this case, a substance having a high removal ability produced by the reaction also functions as a removal auxiliary substance.

  An example of such a removal auxiliary substance is carbon. In this case, as the processing gas, for example, a gas generated by exposing carbon as a removal auxiliary substance to water vapor can be used. The water vapor to which carbon is exposed is preferably 800 ° C. or higher. In this case, for example, it is considered that carbon is exposed to water vapor by bubbling water vapor to carbon. As a result, the reaction between water and carbon produces carbon monoxide gas, which has a higher removal ability than water vapor, thereby assisting the removal reaction with water vapor and increasing the reactivity of the removal reaction over that of water vapor alone. The surface oxide film 11 can be removed at a temperature lower than 300 ° C. In this case, cooling may be performed so that the gas generated by bubbling is supplied to the wafer at a temperature lower than 300 ° C.

  Alkene can be mentioned as a removal auxiliary substance which can improve the reactivity at the time of removing a surface oxide in this way. Specifically, ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, isobutylene, liquid 1-pentene, 1-hexene, 1-heptene, 1-octene, which are gases at room temperature 1-nonene, 1-decene, cis-2-pentene, trans-2-pentene, 3-methyl-1-butene, 2-methyl-2-butene, 2,3-dimethyl-2-butene, etc. are applicable. is there. In the same way as carbon described above, these coexist with water vapor to generate a treatment gas having a higher removing ability than water vapor, thereby assisting the removal reaction with water vapor. Alkenes such as ethylene and propylene can be mentioned. In the same manner, by coexisting with water vapor, a substance having higher removability than water vapor is generated, thereby assisting the removal reaction with water vapor. In this case, the processing gas may be only water vapor and alkene, but may contain diborane, hydrogen peroxide, ammonia or amine in addition to alkene, or may contain ozone in addition to alkene. . As the amine used in this case, methylamine, dimethylamine, trimethylamine and ethylamine which are gases at room temperature can be applied. In addition, diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri- n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, cyclohexylamine, benzylamine, α-phenylethylamine, β-phenylethylamine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, aniline , Methylaniline, dimethylaniline, diphenylaniline, triphenylaniline, o-toluidine, m-toluidine, p-toluidine, o-anisidine, m-anisidine, p-a It can chlorhexidine, o- phenylenediamine, m- phenylenediamine, also be used p- phenylenediamine.

  In addition, acetal and alkyne, as well as epoxide and metal alkoxide can be used as a removal auxiliary substance added to water vapor. By coexisting with water vapor, these also generate a processing gas having a higher surface oxide removal ability than water vapor, thereby assisting the removal reaction with water vapor. Examples of the acetal include acetone dimethyl acetal and dimethyl acetal. Moreover, as alkyne, acetylene, propyne, 1-butyne, 1-pentyne, 1-hexyne, 1-heptin, 1-octyne, 1-nonine, 1-decyne, 2-butyne, 2-pentyne, 3-methyl Examples include -1-butyne, 2-hexyne, 3-hexyne, 3,3-dimethyl-1-butyne, 4-octyne, and 5-decyne. Further, as the epoxide, ethylene oxide, propylene oxide, butylene oxide and the like can be used, and as the metal alkoxide, TEOS (tetraethoxysilane), titanium tetraethoxide and the like can be used.

  As described above, the surface oxide film 11 can be removed at a lower temperature by using a processing gas containing water vapor and a removal auxiliary substance having higher removal ability than water vapor as compared with the case of removing water vapor alone with conventional water vapor. Therefore, damage to the Cu film 5 and the Low-k film 3 can be reduced.

  Next, more specific embodiments of the present invention will be described. FIG. 2 is a schematic sectional view showing an example of a processing apparatus for carrying out the processing method of the present invention. The processing apparatus 100 is configured to supply a gas composed of water vapor and a removal auxiliary substance to the wafer to remove the surface oxide film of the Cu film on the wafer W.

  The processing apparatus 100 is hermetically configured and has a chamber 20 into which a wafer W is loaded. A susceptor 21 for placing a wafer W, which is a substrate to be processed, is provided at the bottom of the chamber 20. A heater 22 for heating the wafer W is embedded in the susceptor 21. A heater power source 22 a is connected to the heater 22.

  A shower head 23 is provided above the susceptor 21 so as to face the susceptor 21. The shower head 23 is supported on the upper portion of the chamber 20, has a gas diffusion space 24 inside, and has a plurality of discharge holes 25 for discharging a processing gas on the surface facing the susceptor 21. A gas introduction port 26 is provided on the upper surface of the shower head 23, and a gas supply pipe 41 from a processing gas supply unit 40 described later is connected to the gas introduction port 26.

  An exhaust port 27 is formed in the bottom wall 20 a of the chamber 20, and an exhaust pipe 28 is connected to the exhaust port 27. The exhaust pipe 28 is connected to an exhaust device 29 provided with a vacuum pump, and is configured so that the inside of the chamber 20 can be evacuated to a predetermined reduced pressure atmosphere. Further, on the side wall of the chamber 20, a loading / unloading port 30 for loading / unloading the wafer W and a gate valve 31 for opening / closing the loading / unloading port 30 are provided.

  The processing gas supply unit 40 includes a hydrogen gas supply source 42 that supplies hydrogen gas and an oxygen gas supply source 43 that supplies oxygen gas, which are supplied to a water vapor generator 44 to generate water vapor. A hydrogen gas pipe 45 extends from the hydrogen gas supply source 42, and an oxygen gas pipe 46 extends from the oxygen gas supply source 43, and these are respectively connected to the water vapor generator 44. An open / close valve 47 and a mass flow controller (MFC) 48 for flow rate control are connected to the hydrogen gas pipe 45. Further, an open / close valve 49 and a mass flow controller (MFC) 50 are connected to the oxygen gas pipe 46. As the water vapor generator 44, various conventionally known ones can be used. In addition to the method of using the water vapor generator 44, methods for supplying the water vapor gas include methods such as bubbling, gas pressure feeding, and heat vaporization, but the case of using a water vapor generator will be described below.

  Further, the processing gas supply unit 40 has a removal auxiliary substance supply mechanism 51. As this removal auxiliary substance supply mechanism 51, a mechanism having a mechanism suitable for the above-described removal auxiliary substance is used. For example, an appropriate method is adopted among methods such as bubbling, gas pressure feeding, and heat vaporization. Hereinafter, the case where heating vaporization is used will be described. Water vapor from the water vapor generator 44 and the removal auxiliary substance heated and vaporized by the removal auxiliary substance supply mechanism 51 are supplied to the reaction promoting chamber 52 to promote these reactions. For the reaction promotion chamber 52, a chamber having a mechanism for heating to a temperature higher than the wafer temperature, a chamber having a mechanism for applying excitation energy such as plasma or light, a chamber having a metal or metal compound catalyst therein, or the like is used. Can do. The steam generator 44 and the reaction promotion chamber 52 are connected by a pipe 53, and the removal auxiliary substance supply mechanism 51 and the reaction promotion chamber 52 are connected by a pipe 54. The pipe 54 is provided with an opening / closing valve 55 and a mass flow controller (MFC) 56. The reaction promoting chamber 52 and the gas inlet 26 of the shower head 23 are connected by the pipe 41 described above. The pipe 53 connecting the steam generator 44 and the reaction promoting chamber 52 is not essential, and the steam generator 44 and the reaction promoting chamber 52 may be directly connected.

  In the reaction promoting chamber 52, the reaction between the water vapor and the removal promoting substance is promoted by heating, excitation energy, or catalyst in this way, so that the surface oxidation of the Cu film is performed by introducing the processing gas mixed with these into the chamber 20. The removal rate of the product (copper oxide) can be further increased. If the reactivity can be ensured even if the water vapor and the removal auxiliary substance are independently supplied to the chamber 20, the reaction promoting chamber 52 is not necessarily used. In the reaction promoting chamber 52, it is preferable to make the flow rate of hydrogen gas sufficiently higher than the flow rate of oxygen gas supplied to the steam generator 44 so that the removal auxiliary substance is not exposed to unreacted oxygen gas.

The gas supply unit 40 further includes an inert gas supply source 58. An inert gas supply pipe 59 is connected to the inert gas supply source 58. This inert gas supply pipe 59 is connected to the pipe 41, and the inert gas is a dilution gas for pressure adjustment and the like. As shown in FIG. The inert gas supply pipe 59 is provided with an opening / closing valve 60 and a mass flow controller (MFC) 61. Examples of the inert gas include N ₂ gas, Ar gas, and He gas. An inert gas line can be connected to the pipes 45, 46, and 54 and used as a purge gas. Note that an inert gas supply source is not essential.

  In the above-described example, the configuration in which the removal auxiliary substance is supplied from the removal auxiliary substance supply mechanism 51 has been described. However, a solid or liquid removal auxiliary substance is installed in the reaction promotion chamber and water vapor is supplied to the reaction promotion chamber. Then, the processing gas may be reacted. An example of a specific method of installing the removal auxiliary substance in the reaction promoting chamber includes a method of coating the removal auxiliary substance on the reaction promoting chamber surface. Alternatively, as shown in FIG. 3, a processing gas supply unit 40 ′ configured to bubble the removal auxiliary substance with water vapor gas may be used. In other words, the processing gas supply unit 40 ′ functions as a powder or liquid removal auxiliary substance storage container 81 and a bubbling mechanism for supplying water vapor to the removal auxiliary substance stored in the storage container 81 for bubbling. And a processing gas supply pipe 83 for supplying the processing gas generated by exposing the removal auxiliary substance to the water vapor by bubbling the removal auxiliary substance into the chamber 20. The steam supply mechanism is not particularly limited, and a steam generator 44 shown in FIG. 2 can be applied. Also in this case, it is preferable that the flow rate of the hydrogen gas is sufficiently higher than the flow rate of the oxygen gas supplied to the steam generator 44 so that the removal auxiliary substance is not exposed to the unreacted oxygen gas. In such a processing gas supply unit 40 ′, when the removal auxiliary substance is carbon, a processing gas containing water vapor and carbon monoxide gas can be obtained relatively easily.

  Each component such as a valve, a mass flow controller, a heater power supply 22a, and an exhaust device 29 in the processing apparatus 100 is controlled by a control unit 70 including a microprocessor. The control unit 70 includes a storage unit that stores a process recipe, an input unit, a display, and the like.

  In the processing apparatus configured as above, first, the gate valve 31 is opened, and the wafer W having the structure shown in FIG. 1A is loaded into the chamber 20 from the loading / unloading port 30, and on the susceptor 21. Place. The susceptor 21 is held at a predetermined temperature lower than 300 ° C. by the heater 22. Then, the inside of the chamber 20 is exhausted through the exhaust port 27 and the exhaust pipe 28 by the exhaust device 29 to bring the inside of the chamber 20 into a predetermined reduced pressure state.

In this state, water vapor and any one of the above-described removal auxiliary substances are supplied from the gas supply unit 40 to the reaction promoting chamber 52, and a processing gas mixed with these is supplied to the wafer W on the susceptor 21 through the shower head 23. To do. In this case, the pressure may be adjusted by supplying an inert gas such as N ₂ gas, Ar gas, or He gas as a diluent gas from the inert gas supply source 58.

  In this way, when the wafer W is brought into contact with the wafer W by a processing gas comprising water vapor and a removal auxiliary substance, in addition to the removal reaction by water vapor, the removal auxiliary substance having a higher ability to remove an oxide film and higher reactivity than that. Since the removal of the oxide is promoted, the removal power is enhanced by these synergistic effects, and the surface oxide film 11 of the Cu film 5 can be removed at a lower temperature than in the case of water vapor alone. Specifically, in the case of water vapor alone, a temperature of 300 ° C. or higher is necessary to cause an oxide removal reaction, whereas the surface oxide film 11 is removed at a temperature lower than 300 ° C. It is possible to reduce damage to the Cu film 5 and the Low-k film 3 which are lower layer wirings. In this case, the control unit 70 can control the supply of the processing gas by the processing gas supply unit 40 or the like so that the surface oxide film 11 of the Cu film 5 is appropriately removed. In addition, the surface oxide film 11 of the Cu film 5 can be removed more appropriately by controlling the atmosphere (pressure) in the chamber 20 by exhausting by the exhaust device 29 by the control unit 70. .

  The pressure in the chamber 20 is preferably about 0.1 to 10000 Pa, and the flow rate of the processing gas composed of water vapor and a removal auxiliary substance is preferably about 1 to 1000 mL / min (sccm).

  In addition, from the viewpoint of preventing re-oxidation of the Cu film, after performing the oxide film removal treatment in this way, it is preferable to use the next process without breaking the vacuum. It is preferable to use a multi-chamber type processing apparatus to which these units (chambers) are connected, and to apply a processing apparatus that performs the above-described removal processing as one unit.

  The present invention can be variously modified without being limited to the above embodiment. For example, in the above-described embodiment, the case of removing the oxide film on the surface of the Cu film exposed at the bottom of the via hole in the damascene structure forming process has been described. However, the oxide film on the surface of the Cu film exposed after the CMP (chemical mechanical polishing) process is removed. The present invention can also be applied to the case where the oxide is not limited to Cu, and any oxide can be used as long as the oxide can be removed by water vapor. In the above embodiment, the present invention is applied to the removal of the surface oxide film of the metal part used in the semiconductor device. However, the present invention is not limited to this. Furthermore, the processing apparatus is merely an example, and various types of apparatuses capable of implementing the method of the present invention can be used.

The figure which shows the example of a process of removing the surface oxide film of Cu film | membrane. The schematic sectional drawing which shows an example of the processing apparatus for enforcing the processing method of this invention. The figure which shows the modification of the process gas supply part in the processing apparatus of FIG.

Explanation of symbols

1; Si substrate 3, 8; Low-k film 4, 12; Barrier metal film 5; Cu film (Cu wiring)
6, 9; Hard mask film 7; Etch stopper film 10; Via hole 11; Surface oxide film 13; Cu film (embedded metal)
DESCRIPTION OF SYMBOLS 20; Chamber 21; Susceptor 23; Shower head 24; Heater 29; Exhaust device 40; Gas supply part 44; Water vapor generator 51; Removal auxiliary substance supply mechanism 70; Control part 100; Processing device W ... Semiconductor wafer (object to be processed) )

Claims (18)

  A process gas containing water vapor and a removal auxiliary substance having a higher ability to remove oxide film than water vapor is brought into contact with an object to be processed having a metal portion having an oxide film formed on the surface, and the oxide film is removed. Processing method.   The processing method according to claim 1, wherein the metal portion is made of copper, and the oxide film is copper oxide.   The processing method according to claim 1, wherein the object to be processed is a semiconductor wafer.   The processing method according to claim 1, wherein the removal auxiliary substance is carbon.   The processing method according to claim 4, wherein the processing gas is a gas generated by exposing carbon as the removal auxiliary substance to water vapor.   The treatment method according to claim 5, wherein the water vapor to which the carbon is exposed is 800 ° C. or higher.   The processing method according to claim 5, wherein the carbon is exposed to water vapor by bubbling water vapor onto the carbon.   The processing method according to any one of claims 1 to 3, wherein the removal auxiliary substance contained in the processing gas contains alkene.   The processing method according to claim 8, wherein the processing gas further contains diborane, hydrogen peroxide, and ammonia or an amine.   The processing method according to claim 9, wherein the processing gas further contains ozone.   The processing method according to any one of claims 1 to 3, wherein the removal auxiliary substance contained in the processing gas contains acetal.   The processing method according to any one of claims 1 to 3, wherein the removal auxiliary substance contained in the processing gas contains an epoxide.   The processing method according to any one of claims 1 to 3, wherein the removal auxiliary substance contained in the processing gas includes an alkoxide.   The processing method according to any one of claims 1 to 3, wherein the removal auxiliary substance contained in the processing gas contains alkyne. A processing container for containing a target object having a metal part with an oxide film formed on the surface;
A treatment gas supply mechanism for supplying a treatment gas containing water vapor and a removal auxiliary substance having a higher ability to remove the oxide film than water vapor in the treatment container;
A processing apparatus for removing the oxide film by supplying the processing gas into the processing container and bringing the processing gas into contact with an oxide film formed on a surface of a metal portion of an object to be processed.   The processing apparatus according to claim 15, further comprising an exhaust mechanism for exhausting the inside of the processing container, wherein the oxide film is removed while exhausting the inside of the processing container to form a reduced-pressure atmosphere.   16. The apparatus according to claim 15, further comprising a control unit that controls supply of a processing gas by the processing gas supply unit so that an oxide film formed on a surface of a metal portion of the object to be processed is removed. Item 17. The processing apparatus according to Item 16.   The processing apparatus according to claim 16, further comprising a heating mechanism that heats an object to be processed in the processing container.

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