JP2001271192A - Surface treating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, in a method for cleaning the surface in which the inside and bottom of a hole with a diameter of micron or less consisting of copper or almost of copper, a combination of a treatment in which a vapor phase treatment using expensive chemicals and a liquid phase treatment is necessary, and extremely long handling time and high cost have been required for it. SOLUTION: For cleaning vapor, above treatments water and acetic acid vapor are used, and only with combination of the treatment in a vapor phase, the removal, i.e., the cleaning of organic impurities adhered on the surface having a fine structure is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is covered with a material comprising as constituent elements vapor (H 2 _{O or} D _{2 O)} metals carried out using or gas containing acetic acid (CH ₃ COOH), particularly copper, or copper The present invention relates to a method for treating a damaged surface or a surface in which a material containing copper and another material are mixed. Particularly, it is characterized in that surface treatment including micropores and grooves having a size on the order of microns or less, which is essential for producing various electronic elements, can be performed only in a gas phase.

[0002]

2. Description of the Related Art As one of the major technologies that embody and support the modern information society, there are technologies for manufacturing various electronic devices such as silicon-based semiconductor devices. In these electronic devices, the thicknesses of various films constituting the devices are becoming increasingly thinner in order to achieve higher functions and higher speed. Further, the diameter of a hole opened in these films for wiring between elements such as formed fine transistors is 0.1.
It is as thin as about μm, and the ratio of the hole depth to the hole diameter (aspect ratio) is 10 and more. As described above, the manufacture of a high-performance electronic device requires a comprehensive fine processing technology such as a high-quality thin film forming technology and a high-precision etching technology such as an opening in the thin film. As one of the technologies enabling such fine processing, there is a processing technology of a surface to be grown before growing various films, that is, a so-called cleaning technology. The problem imposed on this technique is to remove foreign substances and impurities present on the surface of various films before film formation and to remove oxides and the like growing on the surface to ensure the surface state before film formation. It is in.

[0003] In general, when the same kind or different kinds of solids are brought into physical contact with each other, the physicochemical or electromagnetic properties of the interface greatly depend on the surface state before the contact. They must be brought into contact immediately after the appropriate surface treatment, ie after cleaning. Since the thicknesses of the various films used in the above-described electronic devices are extremely thin, on the order of micrometers or less, the formation of these thin films is usually carried out by subjecting a desired film species to a gas under normal pressure or reduced pressure. It is generated by plasma, etc., and is deposited on the surface to be formed by chemical vapor deposition, or ions such as argon are incident on a solid surface whose constituent element is the type of film to be formed, and this solid surface A physical vapor deposition method of vaporizing atoms and molecules of the compound and depositing the same on the surface on which a film is to be formed is mainly used. The physicochemical properties of the various thin films formed in the gas phase in this way depend on the state of the surface to be formed before forming these thin films, that is, the presence or absence of fine dust called particles, molecular organic, Concentration of impurities such as metals, presence of other oxides,
Surface roughness It has been clarified that the surface is greatly influenced by the physicochemical condition, and as a result it has a great effect on the electro-magnetic properties of electronic devices. It is thought that it will become more and more important in the future to purify to an appropriate state by a (washing) method.

[0004] Such a surface cleaning method has hitherto been performed using various solutions which can be easily processed in the atmosphere at almost room temperature. For example, a cleaning method using a silicon surface solution that is often used as a substrate when manufacturing an electronic element has a history of nearly 40 years of research, and has improved cleaning capability, cost reduction,
Environmental considerations have been taken.

However, as described above, the current electronic elements are increasingly miniaturized in order to achieve high performance, and accordingly, the diameter and groove of a hole for embedding a wiring metal or the like formed in a thin film. The width is getting smaller and smaller. (Currently, about 0.1 μm) In the cleaning of the surface on which such fine holes and grooves are formed, particularly in the cleaning of the bottom and side wall surfaces of these holes and grooves, the hole diameter and groove width become very narrow. Therefore, with the conventional cleaning method using a solution, the solution cannot enter the holes and grooves, and even if the solution enters, the solution in the holes and grooves cannot be discharged by the pure water treatment performed after the solution treatment. The problem has come to the surface. One method for solving such a problem is a dry (dry) cleaning method in which seeds that contribute to cleaning are supplied not from a liquid phase such as a solution but from a gas phase. in this case,
Species involved in cleaning in the gas phase should easily penetrate into fine holes and grooves on the surface to be cleaned and clean their side walls and bottom surface compared to cleaning using a conventional solution. Is possible. In addition, since this method forms various thin films after cleaning by the above-described physical or chemical vapor deposition method, it is very compatible in terms of equipment as processing performed in the same vapor phase. There are advantages such as the ability to combine two processes in one device, which contributes to cost reduction. For these reasons, especially the dry cleaning method of organic substances, metal impurities and silicon oxide from the silicon surface has been intensively researched and developed, and some techniques have been put to practical use.

In recent years, in order to improve the performance of electronic devices, new materials have been actively introduced in addition to the miniaturization of the devices described above. For example, copper, which is a metal having a lower resistance, is used instead of aluminum, which has been used as a wiring material between elements, and the insulating layer surrounding the wiring is made of silicon oxide film to fluorine-added silicon oxide film or carbon fluoride. A low dielectric constant film such as a film is being introduced. When a wiring structure is actually formed using such a new material (this wiring layer is called a multi-layer wiring structure because the wiring layer has many layers), the process is different from the process using a conventional material. That is, when aluminum as a conventional wiring material is used, aluminum is first formed by a physical vapor deposition method or the like, and only a desired portion is left, and this layer is removed by reactive ion etching. Next, a process of embedding a silicon oxide film or the like, which is an insulating material, in the trench formed by this etching is repeated to form a multilayer wiring structure. on the other hand,
If copper is used as the wiring material, the current technology cannot process copper to a satisfactory level by reactive ion etching, so a silicon oxide film or low dielectric constant insulating film, which is an insulating material, is first deposited. After forming holes and grooves using reactive ion etching only in the area where wiring material is to be embedded, copper is physically and chemically vapor-deposited and electroformed using these holes and grooves. A multilayer wiring structure is formed by repeating these steps called the damascene method of embedding.

When a multilayer wiring structure is formed in this way, it is very important to clean the bottom and side walls of the holes and grooves before embedding metal in the fine holes and grooves in order to obtain low-resistance electrical contact. Become. That is, an organic substance or a metal impurity and an oxide of a material forming the hole bottom (silicon oxide (Si when the hole bottom is silicon) are formed on the surface of the silicon substrate or copper at the bottom of the hole.
O ₂ ), and in the case of copper, monovalent or divalent copper oxide (Cu ₂ O)
Or CuO)), the film formed thereafter grows while involving these impurities and oxides, and as a result, the contact resistance at this interface increases, resulting in a good product of the manufactured electronic element. This leads to a decrease in the rate.
Therefore, a dry cleaning method for removing organic, metallic impurities and silicon oxides adhering to the surface of a silicon substrate particularly when the bottom of the hole is a silicon substrate has been energetically studied. On the other hand, when the bottom of a hole or groove is made of copper, a method of removing organic substances or copper oxide present on the surface by dry cleaning has not yet been sufficiently studied.

Japanese Patent Application Laid-Open No. 10-261715 (hereinafter referred to as Reference 1) relates to a method for cleaning inside a fine hole having copper as a bottom.
). According to this, the surface immediately after the formation of the fine holes is as shown in FIG. That is, an interlayer insulating film 11 such as a silicon dioxide film
When the fine holes are formed by etching the diffusion preventing layer 13 for preventing the diffusion of copper from the copper wiring layer 12, the object to be processed is exposed to an atmosphere in which a gas containing fluorine or carbon is turned into plasma. In addition, carbon fluoride and the like are attached in the fine holes and on the surface of the interlayer insulating film. Further, since the etching of the diffusion prevention layer 13 must be performed excessively in order to surely open the hole, the lower copper surface is also slightly etched,
At this time, the etched copper compound 15 such as copper or copper fluoride is attached to the inside of the fine hole and the surface of the interlayer insulating film 11. Further, an oxidation or fluoride layer 16 of copper is formed on the surface of the copper wiring layer at the bottom of the fine hole. The cleaning step is required to remove the carbon fluoride or copper or copper compound adhering to the inside of the fine hole and the surface of the interlayer insulating film and the oxidation or oxide layer on the copper surface at the bottom of the fine hole. It is an issue.

According to Reference 1, a method for overcoming the problem is as follows. That is, first, hydrogen or oxygen plasma treatment is performed on the object to be cleaned to remove impurities having fluorine or carbon as a constituent element adhering to the surface of the object to be cleaned including the inside of the fine pores. Next, a diluted hydrofluoric acid solution treatment is performed on the object to be cleaned to remove copper or a copper compound adhering to the surface of the interlayer insulating film on the surface of the object to be cleaned or the inner wall of the fine hole. Finally, this is a cleaning method including a series of steps of exposing an object to be cleaned in a hexafluoroacetylacetone (Hhfac) atmosphere to remove a copper oxide constituting a bottom portion in the fine hole.

[0010]

When micropores are cleaned by using the above-mentioned method, hydrogen plasma or oxygen plasma treatment and Hhfac treatment in the gas phase and dilute hydrofluoric acid solution treatment are used. Therefore, there is a problem that the treatment in the liquid phase is required, and it becomes inevitably complicated, and it takes time and effort.

In particular, when the Hhfac treatment is performed at the end of a series of cleaning treatments to remove the oxide on the copper surface, the removal of the oxide can be achieved, but the surface of the carbon fluoride and hydrocarbon constituting the Hhfac is removed from the surface. Residue is feared. Also Hhfac
Being a very expensive drug itself is very disadvantageous in terms of cost.

An object of the present invention is to provide a means for cleaning the copper surface at the bottom of a fine hole, the side wall of the hole, and the surface of an interlayer insulating film by a series of surface treatment methods in a gas phase not including a solution treatment. It is in.

[0013]

Means for Solving the Problems Oxide or carbon fluoride or fluorine on the copper surface at the bottom of the fine hole of the electronic element, and copper adhered to the insulator side wall by reactive ion etching when forming the hole. In order to realize the dry cleaning of copper, first, as a method of removing copper oxide, it was considered to reduce this oxide to copper.

In general, the alkali metal containing hydrogen at the left end of the periodic table of the elements is an element having a reducing property that can easily donate an electron. However, surface treatment using an alkali metal other than hydrogen, such as lithium or sodium, is not possible. Since it itself is a source of contamination, it is not used in the manufacture of electronic devices, and hydrogen (H ₂ ), ammonia (NH ₃ ), or the like is exclusively used as such a reducing gas. Naturally, it is known that copper oxide is easily reduced to copper when heat treatment is performed in a hydrogen or ammonia atmosphere. The chemical reaction in this case is said to be CuO + H ₂ → Cu + H ₂ O or Cu ₂ O + H ₂ → 2Cu + H ₂ O in the case of hydrogen. However, on the copper surface at the bottom of the hole, carbon fluoride, carbon and fluorine are present together with copper oxide, and when heat treatment is performed in an atmosphere of hydrogen or ammonia, the reduction of copper oxide and the conversion of fluorine to hydrogen are performed. Since hydrogen fluoride (HF) is produced by the reaction, removal of copper oxide and fluorine can be expected as a result, but removal of carbon and carbon fluoride cannot be expected.

Usually, in order to remove such carbon or a compound containing carbon, oxygen (O ₂ ) or a gas containing oxygen is turned into plasma, and chemically active species such as oxygen atoms generated therefrom are removed from the plasma region. To the object to be cleaned installed in the downstream area of the gas, and oxidizes the carbon on the surface to produce carbon dioxide (C
O ₂ ) is volatilized and removed from the surface.

In order to simultaneously remove copper oxides and contaminants such as carbon, fluorine and carbon fluoride, the present inventors conducted a treatment in a gas containing water vapor (H ₂ O or D ₂ O). I thought. That is, water vapor is known to act as an oxidizing agent for silicon, which is considered to be due to the fact that silicon oxide (silicon dioxide) is extremely stable. On the other hand, the standard Gibbs energies of formation of copper oxides are -146 and -130 kJ / mol for monovalent and divalent oxides, respectively, and have absolute values compared to those of silicon dioxide (-856 kJ / mol). small,
Further, since its absolute value is smaller than that of water vapor (−229 kJ / mol), it is expected that the copper surface is not oxidized by water vapor even when copper is exposed to a water vapor atmosphere. At this time, 4CuO → 2Cu ₂ O + O ₂ , 2CuO
It is thought that if the treatment is performed at a temperature at which a chemical reaction such as + 2Cu + O ₂ , 2Cu ₂ O → 4Cu + O ₂ occurs, reduction of copper oxide on the surface to be treated, that is, removal of the copper oxide, is possible. Can be

At this time, the standard Gibbs energy of formation of carbon dioxide, which is an oxide of carbon, is -394.
Since kJ / mol and its absolute value are larger than those of water vapor, it is expected to act as an oxidizing agent, indicating that carbon attached to the surface can be removed as carbon dioxide. It is considered that fluorine is removed from the surface as hydrofluoric acid in the same manner as when the object is exposed to a hydrogen atmosphere. In other words, by treating the object in an atmosphere containing water vapor, reduction and removal of the copper oxide on the surface, and removal of carbon, fluorine and the like adhering to the surface can be performed simultaneously. it can.

On the other hand, the removal of copper or a copper compound adhering to the side walls of the fine pores on the surface of the object to be processed or the surface of the interlayer insulating film is performed by changing the copper or the copper compound to a volatile compound. Must be removed from The above-mentioned Hhfac is a compound having an action of changing copper into a volatile compound.

Further, the search for other volatile compounds of copper revealed that the boiling point of copper acetate (II) hydrate was 240 at atmospheric pressure.
° C. This indicates that volatilization occurs at a temperature lower than this under reduced pressure. Acetic acid (CH ₃ COO) is required to produce such a copper compound.
The object may be exposed to an atmosphere containing H). Acetic acid (anhydrous) is a liquid at room temperature (25 ° C.) and atmospheric pressure, but has a boiling point of 118 ° C., so that it can be heated to a higher temperature even at atmospheric pressure, or if it is depressurized even at room temperature, it becomes gas Therefore, if this is supplied to the surface of the object to be processed, gas phase processing becomes possible. Now, when the copper to be removed is a divalent oxide, CuO + 2CH ₃ COOH → (CH ₃ CO ₃
It is considered that copper acetate hydrate generated as O) ₂ Cu · H ₂ O can be volatilized and removed from the surface to be treated. In addition, when it is desired to remove copper monovalent oxide or unoxidized copper itself, it is considered that the treatment can be carried out by supplying water vapor or oxygen simultaneously with acetic acid, thereby removing them. Alternatively, before exposing the object to be processed in an acetic acid atmosphere, the processed object is processed downstream of oxygen plasma or the like to oxidize copper or a copper compound adhering to the surface, and then, in an atmosphere containing acetic acid. Just do it.
Further, acetic acid is sufficiently inexpensive as compared with Hhfac, so that the present method is also advantageous in terms of cost.

From the above, as a method of cleaning the copper surface at the bottom of the fine hole and the surface of the side wall of the hole, first, copper (including the compound) adhering to the side wall of the fine hole and the surface of the interlayer insulating film is treated with acetic acid. Gas or a gas containing Hhfac. Next, in order to remove organic impurities adhering to the surface and to reduce oxides on the copper surface by using an etching process of fluorine, carbon, carbon fluoride, or the like, or the treatment of a gas containing acetic acid or Hhfac, water vapor is removed. The surface of the object to be cleaned may be treated with the gas contained. At this time, after oxidizing copper or a copper compound adhering to the surface of the object to be processed in an oxygen plasma downstream or the like before exposing the object to acetic acid atmosphere in order to make the cleaning effect more reliable, A series of processes may be performed.

[0021]

FIG. 2 shows an example of an apparatus for performing a surface treatment according to the present invention. Reference numeral 21 denotes a supply device for various gases, which includes a gas flow meter, a valve, and the like. From here, various gases or a mixture thereof are supplied to 23 tanks in which 22 objects to be treated are installed. The 23 tanks are made of a material such as stainless steel, aluminum, and quartz.
At this time, in order to control the temperature of the object to be processed, the object to be processed is set on 24 temperature-controllable processing tables. As another method of controlling the temperature of the object, a method of irradiating the object with light may be used. When the gas used for the surface treatment of the present invention is flown under reduced pressure or atmospheric pressure, the gas is exhausted using a 25 exhaust device.

A series of steps such as forming micropores, cleaning the surface by the surface treatment method of the present invention, and embedding a diffusion prevention film (barrier metal) or conductive material in the pores are performed on the object. In order to perform the process without exposure to the atmosphere, the process may be performed using an apparatus in which the respective processing apparatuses are integrated as shown in FIG. In this figure, first, the object to be treated is 3
After being set in one load / unload chamber and transferred to a 33 load lock chamber via a 32 gate valve, this chamber is evacuated. Thereafter, the workpiece is conveyed in a vacuum except during a series of steps. Next, the object to be processed is transferred to the 35 etching step tank through the 34 transfer chamber, and fine holes and grooves are formed on the surface to be processed. Thereafter, the surface of the object to be treated including the inside of the fine holes and the grooves is cleaned in the 36 washing step tank according to the method of the present invention. Between the etching step and the cleaning step, a processing tank for removing a mask material such as a resist required at the time of etching may be added. Further, a series of processing steps of the present invention may be performed by installing a processing tank for each processing. After the surface to be processed is cleaned in this way, a barrier metal or a conductive material is grown on the surface including the fine holes and grooves in the 37 film forming tank on the surface of the object to be processed. After performing such a series of steps without exposing to the atmosphere, the object to be processed is carried out to the 31 load / unload chamber.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

[First Embodiment] As shown in FIG. 4, a 42 titanium layer (10 nm), a 43 titanium nitride layer (40 nm), a 44 copper layer (1 μm) on a 41 silicon substrate, and In order to reduce the copper oxide on the surface covered with the grown 45 copper oxide, treatment is performed for 10 minutes at various temperatures in a steam atmosphere at a pressure of 133 Pa, and X-ray photoelectron spectroscopy (XPS) is performed. The object was transported to the XPS analysis tank without being exposed to the atmosphere, and the state of the surface of the object after the treatment was examined.

FIGS. 5A and 5B show 2p _3/2 (hereinafter referred to as Cu ₂ ) of copper atoms existing near the surface of the workpiece.
p _3/2 ) Spectrum of photoelectrons emitted from orbitals and LMM Auger electrons (hereinafter abbreviated as Cu AES)
The spectrum is shown. First, (a) Cu2p _3/2
Looking at the spectrum (a) before the steam treatment in the photoelectron spectrum, it can be seen that the binding energy is around 932 eV.
A peak is observed around 34.5 eV. This 934.
The peak near 5 eV is derived from CuO, which is a copper divalent oxide, which indicates that a copper oxide is present on the surface of the object. Also, the peak near 932 eV indicates metallic copper (Cu) and copper monovalent oxide (Cu
_Since both of 2O) may be derived, Cu AES spectrum was observed to distinguish them. Looking at the spectrum of (a) of FIG.
Peaks are observed around eV and 569.5 eV, which are derived from CuO or Cu and Cu ₂ O, respectively. From these results, it can be seen that copper oxides such as CuO and Cu ₂ O exist on the Cu film on the surface to be processed before the treatment in the steam atmosphere.

Next, such a surface is placed at 100 ° C., 150 ° C., 200 ° C., 250 ° C. in a steam atmosphere at a pressure of 133 Pa.
The Cu2p _3/2 photoelectron spectrum and the Cu AES electron spectrum after treatment at 300C and 300C for 10 minutes are shown in Figs. 5A and 5B, respectively.
After the treatment at 100 ° C. in FIG.
Both p _3/2 and Cu AES have no significant change compared to the spectrum before the treatment of (a), but in the spectrum of (c) treated at 150 ° C., the Cu2p of (a)
The peak around 934.5 eV in the _3/2 photoelectron spectrum disappeared, and only the peak around 932 eV was found.
567.5 in the Cu AES electron spectrum.
It can be seen that the peak near 569.5 eV has been emphasized compared to the peak near eV. As a result, the divalent oxide (CuO) on the surface to be treated is reduced to Cu ₂ O (4CuO → 2Cu ₂ O + O ₂ ), and the copper oxide present on the surface of the object to be treated is Cu ₂ This indicates that only O has been reached.

At a temperature of 150 ° C. or higher, the Cu2p _3/2 photoelectron spectrum shown in FIG. 4A hardly changes, and has only a peak near 932 eV. On the other hand, in the Cu AES electron spectrum shown in FIG. 2B, the peak near 569.5 eV decreases as the temperature increases, and (f) almost disappears after the treatment at 300 ° C. You can see that. Also this 300
_3/2 photoelectron spectrum and C
It can be seen that the uAES electron spectrum is very similar to the spectrum of the surface of the object (g) after physically cleaning the surface of the object by argon ion bombardment. Since the oxides and the like do not exist on the copper surface after the cleaning by the argon ion bombardment, the heat treatment at about 300 ° C. in an atmosphere of water vapor causes the oxide on the copper surface (especially Cu ₂ O) is in copper is reduced (2Cu
_{2 O} → 4Cu + _{O 2)} that, that indicates that it is possible to remove copper oxide on the surface.

In order to investigate the mechanism of reduction of copper oxide in such a steam atmosphere, the same treatment was performed in various atmospheres. FIG. 6 shows changes in the Cu2p _3/2 photoelectron spectrum and the Cu AES electron spectrum when the object to be processed described in FIG. 4 is treated at various temperatures in an oxygen atmosphere at a pressure of 133 Pa, as in FIG. FIG. In this case, the phenomenon in which CuO existing on the surface after the treatment at 150 ° C. is reduced to Cu ₂ O is the same as in the steam atmosphere shown in FIG. 5, but as is clear from the results of the CuAES electron spectrum. As the temperature rises, the peak appearing near 569.5 eV derived from Cu ₂ O increases. This indicates that oxidation of the copper surface proceeds in an oxygen atmosphere.

Similarly, FIG. 7 and FIG. 8 show Cu2p obtained by performing a treatment at various temperatures under a pressure of 133 Pa for 10 minutes in a hydrogen atmosphere and a nitrogen atmosphere, respectively.
FIG. 3 is a diagram showing changes in a _3/2 photoelectron spectrum and a Cu AES electron spectrum. It can be seen that these results and the results in the steam atmosphere shown in FIG. 5 are very similar. That is, CuO existing on the surface after the treatment at 150 ° C. is reduced to Cu ₂ O,
After the treatment at ℃, such Cu ₂ O further contains C
This indicates that oxide is not present on the surface of the object to be treated, such as the surface of copper after physical cleaning by argon ion bombardment.

As described above, even in an atmosphere of nitrogen, which is an inert gas, as in other atmospheres of water vapor or hydrogen, 3 times.
Since reduction of Cu ₂ O to Cu at 00 ° C., that is, removal of copper oxide on the surface is possible, the chemical reaction on the surface of the object to be treated in this case is 2Cu ₂ O → 4Cu + O ₂
It is considered to be. This suggests that water vapor acts as an inert gas that does not become an oxidizing agent for copper, like nitrogen.

Generally, the reduction of copper oxides in a reducing gas such as hydrogen occurs at lower temperatures. FIGS. 9 and 10 show the Cu2p _3/2 photoelectron spectrum and the Cu AES when the treatment was performed at a temperature of 200 ° C. and a treatment time of 10 minutes at various pressures in a hydrogen or nitrogen atmosphere.
FIG. 3 is a diagram showing a change in an electronic spectrum. Is CuO with increasing pressure to Cu ₂ O in the case of hydrogen 9, also Cu ₂ O is reduced to Cu, in particular physical cleaning by argon ion bombardment after the treatment with 87.8kPa A spectrum similar to that of the above case was obtained, indicating that the copper oxide on the surface of the object was completely reduced to copper. On the other hand, looking at the case of nitrogen in FIG. 10, the reduction of Cu ₂ O of CuO existing on the surface before the treatment has occurred, but the Cu pressure was increased even when the pressure of nitrogen was increased as in the case of hydrogen. _No reduction of ₂ O to Cu is observed. That is, FIG. 9 when the temperature of the object to be treated is 200 ° C.
Since reduction of Cu ₂ O to Cu at a relatively high partial pressure of hydrogen, such as (d) and (e), is not observed in the case of nitrogen in FIG. 10, hydrogen itself contributed. Reduction of copper oxide (Cu ₂ O + H ₂ → 2Cu + H ₂ O)
It is considered to be. The reason why such reduction was not clearly observed at 200 ° C. in the case of FIG. 7 in which the treatment was performed at a partial pressure of hydrogen of 133 Pa is considered to be because the concentration of hydrogen on the surface to be treated during the treatment was low. Can be

From the above, it has become clear that copper oxide can be reduced and removed in a gas containing water vapor. It was also confirmed that such copper reduction was possible even in a heavy water (D ₂ O) vapor atmosphere.

[Second Embodiment] The surface of the copper thin film described in FIG. 4 is formed of SiO _{2 which} may be actually used as an interlayer insulating film.
After performing the treatment under the reactive ion etching conditions, cleaning by the surface treatment method of the present invention was performed. The processing conditions of the reactive ion etching are as follows: plasma (electric power: 1 kW) is generated by inductive coupling at a partial pressure ratio of tetracarbon octafluoride (C ₄ F ₈ ) to argon at a total pressure of 1.3 Pa;
At 0 V, the processing time is 10 minutes. After etching under such conditions, the object to be processed was processed downstream of oxygen plasma at a pressure of 13 Pa, and then the surface was cleaned by the surface treatment method of the present invention.

FIG. 11 shows (a) Cu2p _3/2 photoelectron spectrum of the surface of the object to be treated after treatment for 10 minutes at various temperatures in a steam atmosphere at a pressure of 133 Pa;
(B) CuAES electron spectrum, (c) l of carbon atom
Spectrum of photoelectrons emitted from s orbital (hereinafter, Cls) and ls orbital of (d) fluorine atom (hereinafter, Fls)
3 shows a change in the spectrum of the photoelectrons emitted from. First, as is clear from the Cu2p3 _{/ 2} photoelectron spectrum and the Cu AES electron spectrum, CuO and copper fluoride (CuF) exist on the copper surface before the treatment.
In addition, as is clear from the Cls photoelectron spectrum and the Fls photoelectron spectrum, organic contaminants such as carbon fluoride (CF _x ) and hydrocarbons (CH _x ) remain.

Next, when the object is processed in a steam atmosphere, the Cu2p _3/2 photoelectron spectrum and the Cu2p3 _{/ 2}
From the AES electron spectrum, CuO and CuF are reduced from Cu ₂ O to Cu with an increase in the processing temperature,
It can be seen that Cu has been almost completely converted after the treatment at 400 ° C.

At the same time, when looking at the Cls photoelectron spectrum and the Fls photoelectron spectrum, the peak derived from organic contaminants and the like existing on the surface before the treatment showed a peak of 300 ° C.
Disappeared almost completely after the treatment, indicating that these contaminants had been removed from the surface.
That is, the above results show that the surface treatment method of the present invention can remove oxides on the copper surface and remove contaminants adhering to the surface such as fluorine, carbon, and carbon fluoride. .

FIG. 12 shows, for comparison, (a) Cu2p3 _{/ 2} photoelectron spectrum and (b) Cu when the same object to be treated as in FIG. 11 was treated in a hydrogen atmosphere.
Changes in the AES electron spectrum, (c) Cls photoelectron spectrum, and (d) Fls photoelectron spectrum are shown. From now on, as the processing temperature in the hydrogen atmosphere increases, FIG.
As in the case of the water vapor shown in FIG.
It can be seen that Cu has been reduced to Cu via ₂ O and the like, and has been almost completely converted to Cu after treatment at 400 ° C.

However, when looking at the Cls photoelectron spectrum and the Fls photoelectron spectrum, the decrease in peaks derived from organic contaminants and the like existing on the surface before the treatment was slower than that in the case of the steam treatment, and it was 400 ° C. It can be seen that hydrocarbons remain on the surface even after the treatment.

Next, FIG. 13 shows (a) changes in the Cls photoelectron spectrum and (b) the Fls photoelectron spectrum when the object is similarly processed in a nitrogen atmosphere. FIG. 11 shows a state of reduction of CuO and CuF present on the surface of the object before the treatment in the nitrogen atmosphere.
And it was the same as the case of the treatment in the steam or hydrogen atmosphere shown in FIG. FIG. 13 shows that fluorine and carbon remain on the surface even after the treatment at 400 ° C. From the above results, the reduction characteristics of the copper oxide were similar to each other in the water vapor, hydrogen, and nitrogen atmospheres.
It was found that the characteristics of removing fluorine and carbon adhering to the surface were most excellent in the case of water vapor. This is because water has both hydrogen and oxygen as constituent elements, so hydrogen in water molecules acts on fluorine to generate hydrogen fluoride and is removed from the surface, and carbon in water molecules. It is considered that the oxygen is acting to generate carbon dioxide and remove it from the surface.

[Third Embodiment] The surface treatment method of the present invention was applied to the removal of copper adhering to the surface of a workpiece. When copper impurities to be removed are attached to the surface of copper or a copper thin film, it is difficult to distinguish between the impurity copper and the underlying copper. Therefore, an attempt was made to remove copper by attaching copper to a silicon substrate.

The object to be treated was prepared as follows. That is, a single crystal substrate of silicon was mixed with 1 cc of a standard solution of copper (copper concentration: 1000 ppm) for atomic absorption analysis to obtain 100 cc of 1 cc.
After being immersed in a 10% by weight hydrofluoric acid solution for 10 minutes to attach copper to the surface, rinsing with ultrapure water is performed, and then 30% by weight at 50 ° C.
Was treated in a hydrogen peroxide solution (H ₂ O ₂ ) for 10 minutes to form an oxide layer of about 1 nm on the silicon surface, and at the same time the copper adhering to the silicon surface was oxidized. The meaning of the oxidation by the hydrogen peroxide solution treatment is that the material of the interlayer insulating film constituting the side wall of the actual fine hole to which the impurity of copper is attached is often silicon dioxide or a material based on silicon dioxide. ,
This is where the silicon surface is oxidized to form such an oxide layer. Therefore, a plasma treatment of a gas containing oxygen may be performed instead of the hydrogen peroxide solution treatment.

With respect to the object thus produced,
The treatment was performed at 200 ° C. in an acetic acid atmosphere at a pressure of 40 Pa. FIG. 14 shows a Cu2p3 _{/ 2} photoelectron spectrum of copper present on the surface of the object with an increase in the processing time at that time. As is apparent from this figure, the intensity of the peak derived from CuO, which appears near 933 eV, decreases as the processing time increases. Then, it was recognized that this peak disappeared in the processing time of 20 minutes, which is considered that the copper impurity existing on the surface of the object was removed from the surface.

Similarly, when acetic acid and oxygen, or acetic acid and water vapor were each processed at a partial pressure ratio of 1, a total pressure of 70 Pa, and an object temperature of 200 ° C., copper impurities were removed in a processing time of 10 minutes. Was completed.

With the removal of copper, the Cls photoelectron spectrum shows that impurities such as hydrocarbons, which are considered to be caused by the treatment in an atmosphere containing acetic acid, are observed on the surface of the object to be treated. Similarly, these could be completely removed by treating for 5 minutes in a steam atmosphere at a temperature of 200 ° C. and a pressure of 133 Pa.

[Fourth Embodiment] An attempt was made to clean a surface having fine holes as shown in FIG. 1 by using the surface treatment method of the present invention. The object to be treated was prepared as follows. That is,
First, a titanium layer (10 nm) and a titanium nitride layer (40 nm) are formed on a silicon substrate, and a copper layer (1 μm) is further formed thereon.
m), a silicon nitride layer (10 nm) as a diffusion preventing layer, and a fluorine-added silicon dioxide layer (2 μm) as an interlayer insulating film were sequentially formed. Next, holes having a diameter of 0.7 μm were formed in the interlayer insulating film at an opening ratio of 30% by reactive ion etching using a mixed gas of tetracarbon tetrafluoride and argon. Thereafter, the silicon nitride layer exposed at the bottom of the hole opened in the interlayer insulating film is etched by reactive ion etching using a mixed gas of methane trifluoride (CHF ₃ ) and argon to expose the underlying copper layer. did.

From the results of the angle-resolved XPS measurement, it was found that carbon fluoride, hydrocarbons, copper fluoride, copper oxide, and the like are present on the surface of the interlayer insulating film and the pores formed on the surface of the workpiece thus formed. confirmed. Therefore, first, in order to remove the copper adhering to the surface of the interlayer insulating film and the side wall in the hole, a pressure of 70 ° C.
The object was subjected to a treatment at 150 ° C. for 10 minutes in an acetic acid atmosphere of Pa. As a result of XPS examination of the surface state after this treatment, no signal derived from copper adhering to the interlayer insulating film and the side wall surface of the hole was observed, and it was confirmed that these coppers were removed by this treatment. found. Next, the surface of the interlayer insulating film,
Removal of organic contaminants such as carbon fluoride and hydrocarbon remaining in the pores and copper oxides present on the copper surface at the bottom of the pores.
The treatment was performed in a steam atmosphere at a pressure of 133 Pa at 300 ° C. for 20 minutes. When the surface after the treatment was evaluated using XPS, it was found that these organic impurities and copper oxide were completely removed.

[0047]

As described above, according to the surface treatment method of the present invention, the surface having fine holes and grooves can be cleaned by performing the treatment only in the vapor phase containing steam or acetic acid. . Liquid phase and gas phase of the conventional method, compared with the process of combining both processes, requires less trouble, and also performs the etching and film forming process performed in the other gas phase and the surface treatment method of the present invention. It is possible to combine the devices, which contribute to cost reduction. Further, the gas used is sufficiently inexpensive as compared with the conventional method. Obviously, the surface treatment method of the present invention is not limited to cleaning a surface having fine holes and grooves.
In other words, it is effective for cleaning the entire surface, which is entirely or partially composed of a material containing copper.

[Brief description of the drawings]

FIG. 1 is a view for explaining a state of a surface of a workpiece to which a surface treatment method of the present invention is applied.

FIG. 2 is a diagram illustrating an example of an apparatus for performing the surface treatment method of the present invention.

FIG. 3 is a diagram illustrating an example of an apparatus that performs processes such as etching and film formation including the surface treatment method of the present invention without exposing an object to be processed to the atmosphere.

FIG. 4 is a view for explaining the structure of an object to be treated used for confirming the effect of the surface treatment method of the present invention.

5 is a diagram showing changes in a Cu2p _3/2 photoelectron spectrum and a Cu AES electron spectrum when the object described in FIG. 4 is processed in a steam atmosphere at various temperatures.

FIG. 6 is a diagram showing changes in a Cu2p _3/2 photoelectron spectrum and a Cu AES electron spectrum when the object described in FIG. 4 is treated in various conditions at an oxygen atmosphere.

FIG. 7 is a diagram showing changes in a Cu2p _3/2 photoelectron spectrum and a Cu AES electron spectrum when the object to be processed described in FIG. 4 is processed at various temperatures in a hydrogen atmosphere.

FIG. 8 is a diagram showing changes in a Cu2p _3/2 photoelectron spectrum and a Cu AES electron spectrum when the object described in FIG. 4 is processed in a nitrogen atmosphere at various temperatures.

FIG. 9 is a diagram showing changes in a Cu2p _3/2 photoelectron spectrum and a Cu AES electron spectrum when the object described in FIG. 4 is processed in a hydrogen atmosphere at various pressures.

FIG. 10 is a diagram showing changes in a Cu2p _3/2 photoelectron spectrum and a Cu AES electron spectrum when the object described in FIG. 4 is processed in a nitrogen atmosphere at various pressures.

FIG. 11 is a graph showing a pressure of 133 after the reactive ion etching and the oxygen plasma treatment are performed on the copper surface described in FIG.
(A) Cu2p _3/2 photoelectron spectrum, (b) CuAES electron spectrum of the surface of the object after treatment for 10 minutes at various temperatures in a steam atmosphere of Pa
It is a figure which showed the change of (c) Cls photoelectron spectrum and (d) Fls photoelectron spectrum.

FIG. 12 shows a pressure 133 after performing reactive ion etching and oxygen plasma treatment on the copper surface described in FIG.
(A) Cu2p _3/2 photoelectron spectrum, (b) CuAES electron spectrum of the surface of the object after being treated at various temperatures for 10 minutes in a hydrogen atmosphere of Pa
It is a figure which showed the change of (c) Cls photoelectron spectrum and (d) Fls photoelectron spectrum.

FIG. 13 shows a pressure 133 after performing reactive ion etching and oxygen plasma treatment on the copper surface described in FIG.
FIG. 6 is a diagram showing changes in (a) Cls photoelectron spectrum and (b) Fls photoelectron spectrum on the surface of the object after treatment for 10 minutes at various temperatures in a nitrogen atmosphere of Pa.

FIG. 14 is a diagram showing a state of a change in a Cu2p3 / 2 photoelectron spectrum of a surface of a silicon substrate to which copper is adhered when the surface is treated in an acetic acid atmosphere.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Interlayer insulating film 12 Copper wiring layer 13 Diffusion prevention film 14 Carbon fluoride 15 Copper or copper compound 16 Copper oxidation or fluoride layer 21 Gas supply device 22 Workpiece 23 Tank 24 Processing table 31 Load / unload chamber Reference Signs List 32 Gate valve 33 Load lock chamber 34 Transfer chamber 35 Etching step tank 36 Cleaning step tank 37 Film forming tank 41 Silicon substrate 42 Titanium layer 43 Titanium nitride layer 44 Copper layer 45 Copper oxide

Continued on the front page (72) Inventor Hiroki Ogawa 2-18-18 Shin-Yokohama, Kohoku-ku, Yokohama-shi, Kanagawa 1st Century Shin-Yokohama Room 701 (72) Inventor Jun Kikuchi 2--14-6 Shirokanedai, Minato-ku, Tokyo F-term (reference) 4K053 PA06 QA01 QA04 RA02 RA04 SA01 TA01 TA04 TA09 XA01 4K057 DA01 DB04 DD03 DE06 DE14 DM02 DM36 DN01 5F004 AA09 AA14 BB17 BB18 CB02 DA00 DA23 DA24 DA26 DB13

Claims (12)

[Claims] 1. A method according to claim 1, wherein said water vapor (H ₂ O) or heavy water vapor (D ₂
A surface treatment method comprising exposing an object to be treated such that copper or a material containing copper as a main component occupies at least a part of the surface in a gas containing O). 2. The surface treatment method according to claim 1, wherein the temperature of the object to be treated during the treatment is particularly 300 ° C. or higher. 3. A surface treatment method comprising exposing an object to be treated to a gas containing acetic acid (CH ₃ COOH). 4. A surface treatment method comprising exposing an object to be treated to a gas containing acetic acid and oxygen. 5. A surface treatment method comprising exposing an object to be treated to a gas containing acetic acid and water vapor. 6. A surface treatment method according to claim 3, wherein the temperature of the object to be treated during the treatment is particularly 150 ° C. or higher. 7. A surface treatment method according to claim 3, wherein copper or a compound containing copper is attached to at least a very small portion of the surface of the object to be treated. 8. The surface treatment method according to claim 3, wherein the treatment according to claim 3 is performed after exposing the surface of the treatment object to an oxidizing atmosphere. 9. The surface treatment method according to claim 8, wherein the oxidizing atmosphere is generated by oxygen plasma. 10. A surface treatment method, comprising: applying the surface treatment according to claim 1 to the object after applying the surface treatment according to claim 3 to the object. 11. The method according to claim 1, wherein the object to be processed is exposed to an atmosphere of a gas containing hexafluoroacetylacetone.
A surface treatment method characterized by applying the surface treatment described in (1) to an object to be treated. 12. An object to be processed which is annealed while exposing the object in which copper or a material mainly composed of copper occupies at least a part of the surface to a gas containing hydrogen or ammonia. 2. A surface treatment method comprising: applying the surface treatment according to claim 1 to an object to be treated.