JP4334070B2 - Method for selective formation of copper coating - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for selectively forming a copper coating.
[0002]
[Prior 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 problems such as signal delay and increased power consumption due to heat generation. For this reason, Cu attracts attention as a next-generation wiring material.
[0003]
In many cases, the Al wiring is formed by a dry etching technique using a chlorine-based gas such as Cl ₂ or BCl _{3 in} the case of LSI, and a wet etching technique in the case of a liquid crystal display device. However, Cu dry etching is realized only in a high-temperature atmosphere, and is not practical at this stage. On the other hand, although it is possible to wet-etch Cu, it is difficult to perform microfabrication.
[0004]
As described above, Cu is difficult to form wiring by etching. Therefore, in the manufacture of LSI, forming Cu wiring by CMP (Chemical Mechanical Polishing) has been partially put into practical use.
[0005]
[Problems to be solved by the invention]
However, when CMP is applied to the wiring formation of a liquid crystal display device, since the substrate of the liquid crystal display device has a large area, it is practically difficult to form a Cu wiring by CMP. Further, even if Cu etching or CMP is possible in the liquid crystal display device, since the area of the Cu wiring is smaller than the area of the glass substrate, most of the Cu film formed on the glass substrate is removed. . As a result, there is a problem that the use efficiency of Cu, which is expensive as a raw material, becomes very low, and the price of the liquid crystal display device increases.
[0006]
The present invention provides a method for selectively forming a copper film that can selectively reduce the cost of raw materials by selectively depositing copper in a region where a base made of an arbitrary material such as a metal or an insulating material is required. It is something to try.
[0007]
[Means for Solving the Problems]
The method for selectively forming a copper film according to the present invention includes a step of forming a conductor pattern made of a material other than copper in a copper film formation scheduled region on the surface of a base film on a substrate and having a higher conductivity than the base film. When,
A step of selectively irradiating the thin film corresponding to the conductor pattern with UV light after forming a thin film of a silane coupling agent or a surfactant on the entire surface;
And a step of selectively depositing a copper film on the conductor pattern by performing CVD of copper.
[0010]
In the method for selectively forming a copper film according to the present invention, it is preferable to perform the CVD of the copper at a temperature of 220 ° C. or lower.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the method for selectively forming a copper coating according to the present invention will be described in detail.
[0012]
(First step)
First, a conductor pattern made of a material other than copper and having a higher conductivity than that of the base film is formed in a region where the copper film is to be formed on the surface of the base film on the substrate.
[0013]
As the substrate, for example, a silicon substrate, a compound semiconductor substrate, a glass substrate, or the like can be used.
[0014]
The base film is made of any material such as single crystal silicon, polycrystalline silicon, amorphous silicon, or an insulator such as silicon oxide or silicon nitride, or a metal such as Ti.
[0015]
The conductor pattern is selected from materials having higher conductivity than the base film, and includes, for example, 5 × 10 ¹⁸ Ti, W, Mo, Ta, Al, or alloys thereof, or n-type or p-type dopants. Made of amorphous silicon or polycrystalline silicon containing at least / cm ² .
[0016]
The conductor pattern preferably has a thickness of 0.01 to 0.2 μm.
[0017]
The conductor pattern is formed, for example, by forming a thin film made of the material on the base film by vacuum deposition, sputtering, CVD, or plating, and then forming a resist pattern on the copper film formation planned area of the thin film by photolithography. Further, the thin film is selectively removed by dry etching or wet etching using the resist pattern as a mask. However, when a very thin thin film of 0.01 to 0.05 μm is used, it is allowed to form a conductor pattern by etching back the thin film by a CMP technique.
[0018]
(Second step)
Next, copper CVD is performed to selectively deposit a copper film on the conductor pattern of the base film.
[0019]
As a raw material gas for CVD of copper, trimethylvinylsilane-added hexafluoroacetyl acetonato kappa, trimethylphosphine-added hexafluoroacetyl aceton kappa, 1,5-cyclooctadiene added hexafluoroacetyl aceton kappa, or the like can be used. . This source gas is allowed to be diluted with a carrier gas such as nitrogen.
[0020]
In the copper CVD, it is desirable to perform an adsorption decomposition reaction of the copper source gas at 220 ° C. or lower, more preferably 150 to 200 ° C.
[0021]
In the method for selectively forming a copper film according to the present invention, after the formation of the conductor pattern, a thin film of a silane coupling agent or a surfactant is formed on the entire surface before the CVD of the copper, and then the conductor pattern is formed. It is allowed to selectively irradiate the corresponding thin film with UV light.
[0022]
Examples of the silane coupling agent include hexamethyldisilazane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxy. Propylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, bis (3-triethoxysilylpropyl) tetrasulfane, etc. Can be mentioned.
[0023]
As the surfactant, a long-chain alkyl sulfonic acid, a long-chain alkyl carboxylic acid, or the like can be used.
[0024]
The thin film of the silane coupling agent or surfactant is formed by, for example, a vapor adsorption method or a coating method. Such a thin film is preferably of a molecular level thickness from the viewpoint of hydrophilization by UV irradiation described later.
[0025]
When the wavelength is 365 nm, it is preferable that the UV light is selectively applied to the coating with an output of 300 mJ / cm ² or more.
[0026]
In addition, in the method for selectively forming a copper film according to the present invention, after the formation of the conductor pattern, an opening is formed in a region corresponding to the conductor pattern on the surface of the base film including the conductor pattern before the CVD of copper. It is allowed to form a photosensitive resin layer.
[0027]
As the photosensitive resin, either a positive type or a negative type can be used. Specifically, a cresol novolac resist, an acrylic resin resist, and the like can be given.
[0028]
The thickness of the photosensitive resin layer is from the viewpoint of improving the separability from the Cu film on the base film when Cu is also deposited on the photosensitive resin layer in Cu CVD described later. It is desirable that the thickness be 3 μm or more, more preferably 0.7 to 1.5 μm.
[0029]
As described above, when a conductor pattern having a higher conductivity than that of the base film is formed in the copper film formation planned region on the surface of the base film on the substrate, the conductor pattern and other than this are formed. There is a difference in charge exchange (mainly adsorption decomposition reaction) with the copper source gas, which will be described later, with the region of the base film. In other words, the conductor pattern facilitates exchange of charges (mainly adsorption decomposition reaction) with the copper source gas as compared with the other underlying film regions. By performing copper CVD (adsorption decomposition reaction of copper source gas) at a low temperature such as 150 to 220 ° C. in such a state, copper is selectively applied to the conductor pattern (copper film formation scheduled region). It can be deposited to form a copper film (copper pattern) such as copper wiring.
[0030]
That is, the present inventors use trimethylvinylsilane-added hexafluoroacetylacetonate copper as a raw material gas for copper, and set the ambient temperature around the substrate to 150 to 220 ° C. with the CVD apparatus having the structure shown in FIG. As a result, it was confirmed that the raw material gas was not decomposed in the gas phase or the deposition rate was almost negligible.
[0031]
This CVD apparatus includes a quartz reaction tube 2 having an inner diameter of 50 mm and having a source gas supply tube 1 at one end (right end). The substrate holder 3 is inserted into the reaction tube 2 from the end (left end) opposite to the supply tube 1. The holder 3 has a housing 5 having a front end surface that functions as a substrate holding portion, in which cooling water is circulated inside, and a cooling water discharge portion 4 on a side wall located outside the reaction tube 2. The cooling water introduction pipe 6 is inserted from the rear end of the housing 5 and introduces cooling water. The 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 on the side opposite to the gas supply tube 1. A sealed tube 10 loaded with a thermocouple is inserted from the end of the reaction tube 2 on the side opposite to the gas supply tube 1 into the inside thereof so that the tip is located near the tip surface of the holder 3.
[0032]
In the CVD apparatus shown in FIG. 1, the 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 11 held on the front end surface of the substrate holder 3 is cooled. Next, trifluorovinylsilane-added hexafluoroacetylacetonate copper, which is a copper source gas, is introduced into the reaction tube 2 through the gas supply pipe 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, the variable valve 9 is controlled so that the pressure in the reaction tube 2 is 100 Pa and the flow velocity in the tube 1 is 8 cm / sec. In a state where the evacuation is stable, the heater 7 is energized and heated. The source gas supplied from the gas supply pipe 1 is heated by the heating of the heater 7. It was confirmed by the thermocouple loaded in the shield tube 10 that the source gas was warmed. Further, it was confirmed by a substrate temperature measurement thermocouple (not shown) that the substrate 11 at this time was maintained at a temperature of 30 ° C. or lower.
[0033]
Under the conditions described above, the temperature of the substrate measured 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 shield tube 10 changes. The relationship between the temperature and the deposited film thickness of Cu was obtained. The result is shown in FIG.
[0034]
FIG. 2 shows that significant Cu deposition is not observed when the ambient temperature measured with a thermocouple near the substrate is 200 ° C. or lower. From this fact, it can be seen that under the conditions of Cu deposition at 200 ° C. (in some cases, 220 ° C. or lower), the decomposition of the source gas does not occur in the gas phase, but is exclusively an adsorption decomposition reaction on the substrate surface. Therefore, it can be seen that Cu is deposited under such conditions at a location (conductor pattern) with higher conductivity where the source gas is adsorbed, and as a result, Cu can be selectively deposited.
[0035]
As described above, according to the present invention, the copper film formation planned area on the surface of the base film on the substrate is made of a material other than copper, and has higher conductivity than the base film, that is, the charge with the copper source gas. After forming a conductor pattern that facilitates exchange (mainly adsorption decomposition reaction), copper CVD (adsorption decomposition reaction of copper source gas) at a low temperature such as 150 to 220 ° C. Copper can be selectively deposited on the conductor pattern (the area where copper coating is to be formed). As a result, it is possible to selectively form a copper film (copper pattern) such as a copper wiring in a desired region of the base without consuming unnecessary copper such as etching and CMP.
[0036]
Further, after the formation of the conductor pattern, before the CVD of copper, a thin film of a silane coupling agent or a surfactant is formed on the surface of the base film including the conductor pattern to make the surface hydrophobic, and the conductor pattern When the UV light is selectively irradiated to the hydrophobic thin film portion where the metal is positioned to make the irradiated region hydrophilic, CVD of copper at a low temperature such as 150 to 250 ° C. By performing the adsorption decomposition reaction, copper can be deposited with high selectivity by the conductor pattern (copper film formation scheduled region) where the hydrophilic thin film is located.
[0037]
Further, after the formation of the conductor pattern, a photosensitive resin layer having an opening in a region corresponding to the conductor pattern is formed on the surface of the base film including the conductor pattern before the CVD of copper. If a hydrophilic / hydrophobic difference is produced between the exposed conductor pattern and the photosensitive resin layer, then subsequent copper CVD (adsorption decomposition reaction of copper source gas) at a low temperature such as 150 to 220 ° C. By carrying out, copper can be deposited with high selectivity by the highly hydrophilic conductive pattern (copper film formation scheduled region). The photosensitive resin layer is removed after selective deposition of copper.
[0038]
【Example】
Hereinafter, preferred embodiments of the present invention (production of an array substrate for TFT-LCD) will be described in detail with reference to the drawings.
[0039]
Example 1
First, an amorphous silicon film having a thickness of 50 nm is formed on a 500 mm × 600 mm glass substrate 21 whose surface is coated with a SiO ₂ film (not shown) for the purpose of preventing contamination by low pressure CVD under a substrate temperature of 420 ° C. A (a-Si) thin film was deposited. Instead of the SiO ₂ film, a silicon nitride (SiN _x ) film or a film made of a mixture of silicon nitride and silicon oxide may be used. Subsequently, an impurity (for example, boron) was doped into the a-Si film for the purpose of controlling the threshold value of the TFT. Subsequently, the boron-doped a-Si film was crystallized by excimer laser annealing to obtain a boron-doped polycrystalline silicon (p-Si) thin film. Note that lamp annealing may be performed instead of the excimer laser annealing. A resist pattern was applied to the surface of the p-Si thin film by spin coating, dried, exposed, and developed to form a resist pattern (not shown). The p-Si thin film 22 was formed by selectively removing the p-Si thin film by CDE (Chemical Dry Etching) using CF ₄ and O ₂ gas using the resist pattern as a mask. After the resist pattern is ashed and removed, a SiO ₂ thin film as a gate insulating film having a thickness of 200 nm is formed on the glass substrate 21 including the island-shaped p-Si thin film 22 by a low pressure plasma CVD method using TEOS as a source gas. 23 was deposited. Subsequently, aluminum was vapor-deposited on the SiO ₂ thin film 23, and a gate electrode 24 was formed as shown in FIG. 3A by selectively etching using a resist pattern (not shown) as a mask.
[0040]
Next, as shown in FIG. 3B, an impurity such as phosphorus is selectively doped into the island-shaped p-Si thin film 22 using the gate electrode 24 as a mask, and the island-shaped p-Si thin film 22 is subjected to n ^+. Type source and drain regions 25 and 26 and a p-type channel region 27 were formed.
[0041]
Next, as shown in FIG. 3C, a silicon nitride (SiN _x ) film 28 as an interlayer insulating film was deposited on the entire surface by low pressure CVD. Subsequently, a resist pattern (not shown) is formed on the silicon nitride film 28, and the silicon nitride film 28 and the SiO ₂ thin film 23 are selectively wet-etched using the resist pattern as a mask. As shown in FIG. 4D, contact holes 29 whose bottoms reach the source and drain regions 25 and 26 are opened.
[0042]
Next, a Ti thin film 30 having a thickness of 0.05 μm was deposited on the entire surface by vacuum evaporation. A resist pattern 31 was formed as shown in FIG. 4E by applying a resist onto the Ti thin film 30 by spin coating, drying, exposing, and developing. Subsequently, the Ti thin film 30 is selectively removed by etching using the resist pattern 31 as a mask, thereby forming Ti patterns 32 and 33 in the contact hole 29 and its peripheral portion as shown in FIG. Then, the resist pattern 31 was ashed and removed.
[0043]
Next, as shown in FIG. 4G, selective CVD is performed under conditions of a substrate temperature of 180 ° C. and a source gas pressure of 1 torr using a trimethylvinylsilane-added hexafluoroacetylaceton kappa that is a copper source gas. Thus, by selectively depositing Cu on the Ti patterns 32 and 33, the source electrode wiring 34 made of Cu and the Ti patterns 32 and 33 connected to the source and drain regions 25 and 26 through the contact holes 29 and The drain electrode wiring 35 was formed to manufacture an array substrate having TFTs.
[0044]
According to the first embodiment, it was possible to manufacture an array substrate having source and drain electrode wirings formed by a Cu selective deposition technique with a small Cu consumption.
[0045]
(Example 2)
After the Ti patterns 32 and 33 are formed by the same method as in the first embodiment, a saturated vapor of hexamethyldisilazane as a silane coupling agent is applied on the silicon nitride film 28 including the Ti patterns 32 and 33 at room temperature ( (25 ° C.) for about 5 minutes. Subsequently, the silane coupling agent thin film portions on the Ti patterns 32 and 33 are selectively irradiated with 365 nm UV light at an output of 1500 mJ / cm ² to cause photolysis of the silane coupling agent. As shown, hydrophilic portions 36 were formed on the Ti patterns 32 and 33. Thereafter, similarly to Example 1, using a trimethylvinylsilane-added hexafluoroacetyl aceton kappa that is a copper source gas, selective CVD is performed under conditions of a substrate temperature of 180 ° C. and a source gas pressure of 1 torr, and a Ti pattern is obtained. By selectively depositing Cu on the source electrode wiring and drain electrode wiring made of Cu, an array substrate having TFTs was manufactured.
[0046]
The obtained array substrate had a source electrode wiring and a drain electrode wiring made of Cu faithful to the Ti pattern.
[0047]
(Example 3)
After Ti patterns 32 and 33 are formed by the same method as in the first embodiment, a positive cresol novolak resist is applied by spin coating on the silicon nitride film 28 including the Ti patterns 32 and 33 and dried. Then, exposure and development were performed to form a 1.0 μm-thick resist layer 38 having openings 37 in regions corresponding to the Ti patterns 32 and 33 as shown in FIG. Subsequently, by using a hexafluoroacetyl acetonato copper added with trimethylvinylsilane, which is a copper source gas, by performing selective CVD under the conditions of a substrate temperature of 200 ° C. and a source gas pressure of 1 torr, FIG. As shown, Cu is mainly deposited on the Ti patterns 32 and 33 exposed from the opening 37 of the resist layer 38 to form the source electrode wiring 34 and the drain electrode wiring 35. At this time, a slight amount of granular Cu 39 was also deposited on the resist layer 38. Subsequently, an array substrate having TFTs shown in FIG. 6C was manufactured by removing the resist layer 38 on which the granular Cu 39 was deposited with an organic solvent.
[0048]
The obtained array substrate had a source electrode wiring 34 and a drain electrode wiring 35 made of Cu faithful to the Ti patterns 32 and 33.
[0049]
In Examples 1 to 3, a Ti pattern was used as the conductor pattern. However, amorphous silicon or polycrystalline silicon containing 5 × 10 ¹⁸ atoms / cm ² or more of other metals or n-type or p-type dopants was used. Even when used, the same selective deposition of copper could be performed.
[0050]
【The invention's effect】
As described above, according to the present invention, it is possible to selectively deposit copper on a necessary region of a base made of an arbitrary material such as a metal or an insulating material to achieve a reduction in raw material cost, etc. It is possible to provide a method for selectively forming a copper film that is effective as a low-resistance wiring of a device.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a low pressure CVD apparatus used for selective formation of a Cu thin film according to the present invention.
FIG. 2 is a graph showing the relationship between the temperature when a Cu thin film is deposited by the low pressure CVD apparatus of FIG. 1 and the thickness of the deposited Cu thin film.
FIG. 3 is a cross-sectional view showing a manufacturing process of an Ares substrate having TFTs in Example 1 of the present invention.
FIG. 4 is a cross-sectional view showing a manufacturing process of an Ares substrate having TFTs in Example 1 of the present invention.
FIG. 5 is a cross-sectional view showing a manufacturing process of an Ares substrate having TFTs in Example 2 of the present invention.
6 is a cross-sectional view showing a manufacturing process of an Ares substrate having a TFT according to Embodiment 3 of the present invention. FIG.
[Explanation of symbols]
1 ... Gas supply pipe,
2 ... reaction tube,
3 ... Substrate holder,
7 ... Heater,
11 ... substrate
21 ... Glass substrate,
22 ... p-Si thin film,
24 ... Gate electrode,
25 ... Source region,
26 ... drain region,
29 ... Contact hole,
32, 33 ... Ti pattern,
34 ... Source electrode wiring,
35 ... Drain electrode wiring,
37 ... opening,
38. Resist layer.

Claims (4)

A step of forming a conductor pattern having a higher conductivity than the base film, made of a material other than copper in the copper film formation scheduled region on the surface of the base film on the substrate;
A step of selectively irradiating the thin film corresponding to the conductor pattern with UV light after forming a thin film of a silane coupling agent or a surfactant on the entire surface;
A method for selectively forming a copper film, comprising: performing CVD of copper and selectively depositing a copper film on the conductor pattern.   2. The method for selectively forming a copper film according to claim 1, wherein the conductor pattern is made of Ti, W, Mo, Ta, Al, or an alloy thereof. ^{2. The} method for selectively forming a copper film according to claim 1, wherein the conductor pattern is made of amorphous silicon or polycrystalline silicon containing 5 × 10 ¹⁸ / cm ² or more of n-type or p-type dopant. 4. The method for selectively forming a copper film according to claim 1, wherein the CVD of copper is performed at a temperature of 220 [deg.] C. or less.

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