JP2001035811A - Method for selectively forming copper film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deposite copper selectively on the copper-film-formation requiring regions of an underlying film and reduce the cost of the raw material of copper, by forming on the surface of the underlying film provided on a substrate the thin-film made of a silane coupling agent or an interfacial active agent, and by projecting UV rays on the copper-film formation prearranging regions of this thin film to perform on these regions the CVDs of copper. SOLUTION: In this method, the thin film made of a silane coupling agent or an interfacial active agent is formed on the surface of an underlying film 22 provided on a substrate 21. The underlying film 22 is formed out of the arbitrary material of such an insulator as single-crystal silicon, such a metal as Cu, or the like. As the silane coupling agent, there are hexamethyldisilazane, vinyltrichlorosilane, and the like. As the interfacial active agent, there can be used long-chain alkylsulfonic acid and long-chain alkylcarboxylic acid. Then, by projecting selectively UV rays on the copper-film formation prearranging regions of this thin film, these regions are made hydrophilic. Subsequently, hexafluoro-acetylacetonate copper having added trimethylvinylsilane thereto is used as the raw material of copper to perform on these regions the CVDs of copper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for selectively forming a copper film.

[0002]

2. Description of the Related Art Aluminum (Al) is mainly used as a wiring material for LSIs and liquid crystal display devices. However, since Al has a higher resistance than copper (Cu),
The Al wiring has a problem that signal delay and heat consumption increase due to heat generation. For this reason, Cu is receiving attention as a next-generation wiring material.

[0003] In the case of LSI, Al wiring is made of Cl ₂ , B
Dry etching with chlorine-based gas such as Cl _3,
In the case of a liquid crystal display device, it is often formed by a wet etching technique. However, dry etching of Cu is realized only in a high-temperature atmosphere, and is not practical at this stage. On the other hand, although Cu can be wet etched, it is difficult to perform fine processing.

[0004] As described above, Cu is difficult to form wiring by etching.
Forming a Cu wiring by MP (Chemical Mechanical Polishing) has been partially put to practical use.

[0005]

SUMMARY OF THE INVENTION However, CMP
Is applied to the formation of wiring of a liquid crystal display device, it is practically difficult to form Cu wiring by CMP because the substrate of the liquid crystal display device has a large area. Even if Cu etching or CMP is possible in the liquid crystal display device, most of the Cu film formed on the glass substrate is removed because the area of the Cu wiring is smaller than the area of the glass substrate. . As a result, there is a problem that the use efficiency of Cu, which is expensive as a raw material, becomes extremely low, and the price of the liquid crystal display device rises.

According to the present invention, there is provided a method for selectively forming a copper film capable of achieving a reduction in raw material cost by selectively depositing copper in a required area of a base made of an arbitrary material such as a metal and an insulating material. It seeks to provide a way.

[0007]

According to the present invention, there is provided a method for selectively forming a copper film, comprising the steps of forming a thin film of a silane coupling agent or a surfactant on the surface of a base film on a substrate; A step of making the planned region hydrophilic by selectively irradiating UV light or the like; and a step of performing copper CVD to selectively form a copper film in the copper film formation planned region of the base film. It is characterized by the following.

Another method for selectively forming a copper film according to the present invention includes a step of forming a fluorocarbon thin film on a surface of an underlayer film on a substrate by plasma CVD, and a step of selectively applying UV light to a region of the thin film where a copper film is to be formed. Irradiation process and copper CV
D) to selectively form a copper film in the copper film formation region of the underlayer film.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for selectively forming a copper film according to the present invention will be described in detail.

(First Step) First, a thin film of a silane coupling agent or a surfactant is formed on the surface of a base film on a substrate.

As the substrate, for example, a silicon substrate,
A compound semiconductor substrate, a glass substrate, or the like can be used.

The base film is formed of any material such as an insulator such as single crystal silicon, polycrystalline silicon, amorphous silicon, silicon oxide, and silicon nitride, and a metal such as Cu and Ti.

As the silane coupling agent, for example, hexamethyldisilazane, vinyltrichlorosilane,
Vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-
Glycidoxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-
Examples thereof include aminopropyltriethoxysilane and bis (3-triethoxysilylpropyl) tetrasulfane.

As the surfactant, a long-chain alkyl sulfonic acid, a long-chain alkyl carboxylic acid and the like can be used.

The thin film of the silane coupling agent or the surfactant is formed by, for example, a vapor adsorption method or a coating method. From the viewpoint of decomposing and removing such a thin film by UV irradiation, which will be described later, it is preferable that the thin film has a thickness on a molecular level.

(Second Step) Next, the region of the thin film where the copper film is to be formed is made hydrophilic.

In order to make the region of the thin film where the copper film is to be formed hydrophilic, for example, UV
A method of selectively irradiating light can be employed.

When the wavelength of the UV light is 365 nm,
It is preferable to selectively irradiate the coating with an output of 300 mJ / cm ² or more.

(Third Step) Next, a copper film is selectively deposited on the undercoat film in the region where the copper film is to be formed by CVD of copper.

As a raw material gas for copper CVD, hexafluoroacetylacenatato copper with trimethylvinylsilane added, hexafluoroacetylacenatato copper with trimethylphosphine, hexafluoroacetylacenatato copper with 1,5-cyclooctadiene, or the like is used. be able to. This source gas is allowed to be used after being diluted with a carrier gas such as nitrogen.

In the copper CVD, it is desirable to carry out the adsorption decomposition reaction of the copper raw material gas at a substrate temperature of 220 ° C. or lower, more preferably 150 to 200 ° C.

As described above, when a thin film of a silane coupling agent or a surfactant is formed on the surface of a base film on a substrate, the film becomes hydrophobic. For example, UV light is selectively irradiated to a region where the copper film of the hydrophobic film is to be formed, to make the irradiated region hydrophilic. That is, there is a difference between hydrophobicity and hydrophilicity on the surface of the base film. In such a state, by performing copper CVD (adsorption decomposition reaction of a copper source gas) at a low temperature such as 150 to 220 ° C., copper is selectively formed in the hydrophilic region (copper film formation planned region). To form a copper film (copper pattern) such as a copper wiring.

That is, the inventors of the present invention used hexafluoroacetylacetonate copper with trimethylvinylsilane as a raw material gas for copper, and increased the ambient temperature around the substrate to 150 to 220 ° C. with a CVD apparatus having the structure shown in FIG.
Thus, it was confirmed that the decomposition of the source gas in the gas phase did not occur, or the deposition rate was almost negligible.

This CVD apparatus includes a quartz reaction tube 2 having an inner diameter of 50 mm and a source gas supply tube 1 at one end (right end). The substrate holder 3 is inserted into the reaction tube 2 from an end (left end) opposite to the supply tube 1. The holder 3 has a housing 5 having a front end surface functioning as a substrate holding unit, cooling water circulating therein, and having a cooling water discharge unit 4 on a side wall located outside the reaction tube 2. ,
A cooling water introduction pipe 6 is inserted from the rear end of the housing 5 to introduce cooling water. Heater 7
Is wound around the outer periphery of the reaction tube 2 over a length of about 1 m from the vicinity of the tip of the substrate holder 3 toward the source gas supply tube 1. The vacuum pump 8 is connected through a variable valve 9 near the end of the reaction tube 2 opposite to the gas supply tube 1. Sealed tube 10 loaded with thermocouple
Is inserted from the end of the reaction tube 2 on the side opposite to the gas supply tube 1 so that the end is located near the end surface of the holder 3.

In the CVD apparatus shown in FIG. 1, a substrate 11 made of a desired material is held on the front end surface of the substrate holder 3, and cooling water is introduced into the housing 5 through the cooling water introduction pipe 6 and discharged from the discharge unit 4. The substrate holder 3
The substrate 11 held on the tip surface is cooled. Subsequently, trimethylvinylsilane-added hexafluoroacetylacenato copper, which is a copper raw material gas, is introduced into the reaction tube 2 through the gas supply tube 1, and the vacuum pump 8 is operated to change the gas in the reaction tube 2 to a variable valve. Exhaust through 9. At this time, control is performed by the variable valve 9 so that the pressure in the reaction tube 2 becomes 100 Pa and the flow velocity in the tube 1 becomes 8 cm / sec. The heater 7 is energized and heated in a state where the evacuation is stable. The raw material gas supplied from the gas supply pipe 1 is heated by the heating of the heater 7. The fact that the source gas was warmed was confirmed by a thermocouple loaded in the seal tube 10. The substrate 11 at this time is 3
It was confirmed by a substrate temperature measuring thermocouple (not shown) that the temperature was kept at 0 ° C. or lower.

Under the above-described conditions, the cooling of the substrate by the substrate holder and the heating temperature by the heater 7 are controlled so that the temperature measured by the thermocouple loaded in the above-mentioned shield tube 10 changes, and the film is formed for 24 hours. The relationship between the temperature during operation and the deposited film thickness of Cu was determined. The result is shown in FIG.

FIG. 2 shows that no significant Cu deposition was observed when the ambient temperature measured by a thermocouple near the substrate was 200 ° C. or less. From this fact, 200 ° C
It can be seen that under the conditions of Cu deposition (in some cases, 220 ° C. or lower), the decomposition of the source gas does not occur in the gas phase, and is exclusively an adsorption decomposition reaction on the substrate surface. Therefore, the deposition of Cu under such a condition is performed at a hydrophilic portion where the source gas is adsorbed, and the Cu is not deposited at a hydrophobic portion where the adsorption of the source gas is inhibited. It can be seen that a proper deposition can be achieved.

In fact, a saturated vapor of a silane coupling agent (for example, hexamethyldisilazane) is applied to a single-crystal silicon substrate, a polycrystalline silicon substrate, an amorphous silicon substrate, or a single-crystal silicon substrate having a surface coated with an SiO film, at room temperature. (25
C) for about 5 minutes. The length of the adsorption time does not particularly affect the subsequent characteristics. Subsequently, for example, 365 on the surface to which the silane coupling agent is adsorbed.
Irradiated with UV light of 1500 nm at an output of 1500 mJ / cm ² . After irradiation, it was confirmed by XPS analysis that the coupling agent had changed to one in which the Si—O bond was dominant.

Next, each substrate before the treatment with the silane coupling agent, each substrate after the treatment with the silane coupling agent,
And each substrate after the UV light irradiation is held in the substrate holder shown in FIG. 1 described above, using a hexafluoroacetylacetonate copper containing trimethylvinylsilane, which is a raw material gas for copper, at 150 ° C. and a raw material gas pressure of 1 torr. A Cu film was deposited by CVD in the above.

FIG. 3 shows the thickness of the Cu film on each substrate (for 2 minutes). This FIG. 3 suggests an important process advantage. This is because a large amount of C is present between the surface on which the silane coupling agent is adsorbed and the surface irradiated with UV light, regardless of the underlying material.
A difference in film thickness of u occurs, and only UV irradiation controls the deposition region.

As described above, according to the present invention, a thin film of a silane coupling agent or a surfactant is formed on the surface of a base film on a substrate to make the surface hydrophobic, and a copper film is formed on the surface of the hydrophobic film. After selectively irradiating the predetermined area with UV light to make the irradiated area hydrophilic, copper CVD (adsorption decomposition reaction of copper raw material gas) is performed at a low temperature such as 150 to 220 ° C. Copper can be selectively deposited on the hydrophilic region (the region where the copper film is to be formed). As a result, a copper film (copper pattern) such as a copper wiring can be selectively formed in a desired region of the base without wasting copper such as etching or CMP.

Next, another method for selectively forming a copper film according to the present invention will be described in detail.

(First Step) First, a fluorocarbon thin film is formed on the surface of a base film on a substrate by plasma CVD.

As the substrate and the base film, the same ones as described above are used.

(Second Step) Next, UV light is selectively irradiated to a region where the copper film of the fluorocarbon thin film is to be formed. Subsequently, copper CVD is performed to selectively deposit a copper film on the region where the copper film is to be formed in the underlayer.

As the raw material gas for copper CVD, the same gas as described above is used.

In the copper CVD, it is desirable to carry out the adsorption decomposition reaction of the copper source gas at a substrate temperature of 220 ° C. or lower, more preferably 150 to 200 ° C.

As described above, a hydrophobic fluorocarbon thin film is formed on the surface of a base film on a substrate, and a region where a copper film is to be formed is selectively irradiated with UV light to make the irradiated region hydrophilic. . In other words, hydrophobic /
A difference in hydrophilicity occurs. 150-220 ° C in such a state
By performing copper CVD (adsorption decomposition reaction of a copper source gas) at a low temperature as described above, copper is selectively deposited on the hydrophilic region (the region where a copper film is to be formed), for example, as in the case of copper wiring. Copper film (copper pattern) can be formed.

[0039]

FIG. 4 and FIG. 5 show a preferred embodiment of the present invention.
This will be described in detail with reference to FIG.

Example 1 First, as shown in FIG. 4A, a substrate temperature of 500 mm × 600 mm was coated on a glass substrate 21 coated with a SiO ₂ film (not shown) for preventing contamination. An amorphous silicon (a-Si) thin film 22 having a thickness of 50 nm by a low pressure CVD method at 420 ° C.
Was deposited. Note that a silicon nitride (SiN _x ) film or a film made of a mixture of silicon nitride and silicon oxide may be used instead of the SiO ₂ film. Subsequently, as shown in FIG. 4B, a-
The Si film 22 was doped with an impurity (for example, boron). Subsequently, the boron-doped a-Si film was subjected to excimer laser annealing and crystallized to obtain a boron-doped polycrystalline silicon (p-Si) thin film 23. Note that lamp annealing may be performed instead of the excimer laser annealing.

Next, a resist was applied to the surface of the p-Si thin film 23 by spin coating, dried, exposed, and developed to form resist patterns 24 and 25. Subsequently, these resist patterns 24, 2
5 using CF ₄ and O ₂ gas as masks
By selectively removing the p-Si thin film 23 by chemical dry etching, the island-like p-type shown in FIG.
-Si thin films 26 and 27 were formed.

Next, after the resist pattern is ashed and removed, as shown in FIG. 4D, a pressure reduction using TEOS as a source gas is performed on the glass substrate 21 including the island-like p-Si thin films 26 and 27. 200 thickness by plasma CVD
The nm of SiO ₂ film 28 is deposited, was further deposited silicon nitride (SiN _x) film 29 having a thickness of 50nm by vacuum plasma CVD on the SiO ₂ film 28. Subsequently, a resist is applied to the surface of the silicon nitride thin film 29 by a spin coat method, dried, exposed, and developed to form a resist pattern (not shown). The diffusion barrier film 30 shown in FIG. 4E was formed by selectively etching away the thin film 29 and further removing the resist pattern.

Next, the Si containing the diffusion barrier film 30
A saturated vapor of hexamethyldisilazane as a silane coupling agent was adsorbed on the O thin film 28 at room temperature (25 ° C.) for about 5 minutes. UV light of 365 nm is applied to the surface of the diffusion barrier film 30 to which the silane coupling agent is adsorbed for 1500 m.
The silane coupling agent was photodegraded by selective irradiation at an output of J / cm ² . Subsequently, a Cu film is deposited on the diffusion barrier film 30 by selective CVD under conditions of a substrate temperature of 200 ° C. and a source gas pressure of 1 torr using hexafluoroacetylacenato copper to which trimethylvinylsilane as a source gas for copper is added. did. Thereafter, heat treatment was performed to form a gate electrode 31 made of Cu as shown in FIG. This heat treatment is performed to remove moisture adsorbed in the CVD process, but may be omitted.

Next, inspection of the gate electrode 31, that is, C
The resistance value of the u film and the presence or absence of disconnection were electrically inspected, and the disconnection or short circuit was inspected by comparing the contour of the gate electrode 31 with a previously stored pattern. A substrate determined as a non-defective product in this inspection is selected, and as shown in FIG. 5 (g), impurities such as phosphorus are added to the island-shaped p-Si using the gate electrode 31 and the diffusion barrier film 30 thereunder as a mask.
By selectively doping the thin films 26 and 27, each island-shaped p-
N ⁺ -type source and drain regions 3 on Si thin films 26 and 27
2, 33 and a p-type channel region 34 were formed, respectively.

Next, interlayer insulation is performed on the entire surface by a low pressure CVD method.
Silicon nitride (SiN) as edge film _x) Deposit the film 35
Was. Subsequently, the silicon nitride (SiN_x) On membrane 35
A resist pattern (not shown) is formed on the resist.
The silicon nitride (Si
N_x) Selectively wet film 35 and SiO thin film 28
By etching, as shown in FIG.
The bottoms correspond to the source and drain regions 32 and 33, respectively.
The reaching contact hole 36 was opened. Next, this
The silicon nitride (S) including these contact holes 36
iN_x) Al for source and drain electrode wiring on film 35
An -Nd alloy film was deposited by sputtering. this
Then, a resist pattern (not shown) is formed on the Al-Nd alloy film.
Pattern, and using this resist pattern as a mask, C
l_TwoAnd BCl_ThreeReactive ion etching using various gases
The Al-Nd alloy film is selectively etched by etching.
As shown in FIG. 5 (i),
Connected to the source region 32 through the contact hole 36
Through the source electrode wiring 37 and the contact hole 36
And a drain electrode arrangement connected to the drain region 33.
Forming an array substrate having a plurality of TFTs by forming the line 38;
Built.

According to the first embodiment, it was possible to manufacture an array substrate having a gate electrode formed by the Cu selective deposition technique, which consumes a small amount of Cu.

In the first embodiment, the source and drain electrode wirings are formed by sputtering evaporation and patterning of an Al—Nd alloy film, but are formed by a Cu film selective deposition technique substantially similar to the formation of a Cu gate electrode. You may.

(Example 2) First, a silicon wafer having a 100-nm-thick thermal oxide film formed on its surface is placed in a vacuum chamber, and CHF ₃ gas is supplied to this chamber for 10 seconds.
Cm flow rate and chamber pressure 20 mtorr
After that, 800 W of high frequency power was applied to generate inductively coupled RF plasma. By exposing the silicon wafer to such plasma for 30 seconds, a fluorocarbon thin film having a thickness of 20 nm was deposited on the thermal oxide film of the wafer.

Next, UV light having a wavelength of 365 nm was applied to the area where the copper film of the fluorocarbon thin film was to be formed by 20,000 m.
Irradiation was performed at an output of J / cm ² . Subsequently, the wafer was placed in a reaction tube, and 0.1 cc / min of hexafluoroacetylacenato copper with trimethylvinylsilane, which is a copper source gas, and a carrier gas (nitrogen gas) of 1 cc / min.
The gas was introduced under the condition of 00 sccm, and the gas in the reaction tube was exhausted at the same time.
Was performed under the conditions described above.

As a result, a Cu film could be selectively deposited on the UV light irradiation area.

[0051]

As described above, according to the present invention, copper can be selectively deposited on a required area of a base made of an arbitrary material such as a metal and an insulating material, thereby achieving a reduction in material cost and the like. , LSI, and a method for selectively forming a copper film effective as a low-resistance wiring of a liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a reduced pressure CVD apparatus used for selective formation of a Cu thin film of the present invention.

FIG. 2 is a graph showing the relationship between the temperature when depositing a Cu thin film and the thickness of the deposited Cu thin film using the low-pressure CVD apparatus shown in FIG.

FIG. 3 shows the Cu deposition film thickness (2 minutes) of various substrates, various substrates having a silane coupling agent vapor-deposited on the surface, and various substrates having a silane coupling agent vapor-deposited on the surface and further irradiated with UV light. Graph.

FIG. 4 is a cross-sectional view illustrating a process of manufacturing an Ares substrate having a TFT according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a process of manufacturing an Ares substrate having a TFT according to the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gas supply pipe, 2 ... Reaction tube, 3 ... Substrate holder, 7 ... Heater, 11 ... Substrate, 21 ... Glass substrate, 23 ... p-Si thin film, 30 ... Diffusion barrier film, 31 ... Gate electrode, 32 ... Source Region 33: Drain region 36: Contact hole 37: Source electrode wiring 38: Drain electrode wiring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keisaku Yamada 1-9-2 Hara-cho, Fukaya-shi, Saitama F-term in Fukaya Plant, Toshiba Corporation (reference) 4M104 AA01 AA08 AA09 BB02 BB04 CC05 DD43 DD45 DD47 FF21 GG08 GG14 5F033 HH11 PP02 PP08 QQ01 QQ68 VV06 XX08 5F110 AA03 AA16 AA28 BB01 CC01 DD02 DD13 EE02 EE45 EE47 FF02 FF03 FF30 FF32 GG02 GG13 GG32 GG47 GG53 PP03 PP27 PP32 QQ04

Claims (4)

[Claims] A step of forming a thin film of a silane coupling agent or a surfactant on the surface of a base film on a substrate, a step of making a region of the thin film where a copper film is to be formed hydrophilic, and a step of performing copper CVD. Selectively forming a copper film in a region of the base film where the copper film is to be formed. 2. The method according to claim 1, wherein the step of making the copper film formation region of the thin film hydrophilic is performed by selectively irradiating the UV light to the copper film formation region of the thin film. A method for selectively forming a copper film as described in the above. A step of forming a fluorocarbon thin film on the surface of the base film on the substrate by plasma CVD, a step of selectively irradiating a UV light to an area of the thin film where a copper film is to be formed, and performing a CVD of copper. Selectively forming a copper film in a region of the base film where the copper film is to be formed. 4. The method according to claim 1, wherein the CVD of the copper is performed by setting the temperature of the substrate to two.
The method according to any one of claims 1 to 3, wherein the method is performed at a temperature of 20 ° C or lower.