JP4138166B2 - Method for selectively forming copper film and method for manufacturing semiconductor device - 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 total 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. The 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 coating according to the present invention includes a step of forming a thin film having a hydrophobic surface on the surface of a hydrophilic base film on a substrate,
Forming an opening in the copper film formation planned region of the thin film to expose the base film ;
Performing CVD of copper at a substrate temperature of 220 ° C. or lower, and depositing a copper film on the underlying film mainly exposed from the opening of the thin film;
And a step of removing the thin film.
A method of manufacturing a semiconductor device according to the present invention includes a step of forming a thin film having a hydrophobic surface on the surface of a hydrophilic base film on a substrate,
Forming an opening in the copper film formation planned region of the thin film to expose the base film;
Performing copper CVD at a substrate temperature of 220 ° C. or lower, and depositing copper wiring on a base film mainly exposed from the opening of the thin film;
Removing the thin film;
It is characterized by comprising.
[0008]
In the method for selectively forming a copper coating according to the present invention, a photosensitive resin layer is used as a thin film having a hydrophobic surface, and the photosensitive resin layer is exposed and developed at an opening in a region where the copper coating is to be formed. It is preferable to form by this.
[0009]
In the method for selectively forming a copper film according to the present invention, it is preferable to expose the photosensitive resin layer to plasma of O ₂ gas or a mixed gas containing O ₂ gas after exposure.
[0010]
In the method for selectively forming a copper film according to the present invention, it is preferable to expose the photosensitive resin layer to at least one of ozone gas and ultraviolet light after exposure.
[0011]
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.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the method for selectively forming a copper coating according to the present invention will be described in detail.
[0013]
(First step)
First, a thin film having a hydrophobic surface is formed on the surface of the base film on the substrate. Subsequently, an opening is formed in the copper film formation scheduled region of the thin film.
[0014]
As the substrate, for example, a silicon substrate, a compound semiconductor substrate, a glass substrate, or the like can be used.
[0015]
The base film is made of an arbitrary material such as a metal such as Cu or Ti, as well as an insulator such as single crystal silicon, polycrystalline silicon, amorphous silicon, silicon oxide, or silicon nitride.
[0016]
Examples of the thin film having a hydrophobic surface include a photosensitive resin layer. 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. In order to form the opening of the region where the copper film is to be formed in such a photosensitive resin layer, for example, a method of exposing and developing can be employed.
[0017]
The thickness of the thin film (especially the photosensitive resin layer) improves the separability from the Cu film on the base film when Cu is also deposited on this photosensitive resin layer in Cu CVD described later. From the viewpoint, it is desirable that the thickness be 0.3 μm or more, more preferably 0.7 to 1.5 μm.
[0018]
In addition, after exposure of the photosensitive resin layer, exposure to plasma of O ₂ gas or a mixed gas containing O ₂ gas is permitted. As this mixed gas, for example, a mixed gas of CF ₄ and O ₂ can be used. In order to prevent film verification due to ashing of the photosensitive resin layer, it is preferable that the time of exposure to plasma is 1 minute or less. Moreover, you may expose to any one or both of ozone gas or an ultraviolet-ray instead of the process by plasma.
[0019]
(Second step)
Next, copper CVD is performed, and a copper film is mainly selectively deposited on the base film portion (copper film formation planned region) exposed from the opening of the photosensitive resin layer. Thereafter, the photosensitive resin layer is removed, and a copper film (for example, copper wiring) is formed on the base film.
[0020]
As a raw material gas for CVD of copper, trifluorovinyl silane-added hexafluoroacetyl aceton kappa, trimethyl phosphine added hexafluoro acetyl aceton kappa, 1,5-cyclooctadiene added hexafluoro acetyl aceton kappa, etc. can be used. . This source gas is allowed to be diluted with a carrier gas such as nitrogen.
[0021]
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.
[0022]
As described above, a thin film having a hydrophobic surface such as a photosensitive resin layer is formed on the base film, and an opening is formed in a copper film formation scheduled region by performing exposure and development treatment. Since the photosensitive resin is usually hydrophobic, a hydrophilic / hydrophobic difference occurs between the base film exposed from the opening and the photosensitive resin layer. In this state, copper is selected as the hydrophilic underlayer (copper coating formation region) by performing copper CVD (adsorption decomposition reaction of copper source gas) at a low temperature such as 150 to 220 ° C. Is deposited. At this time, since some copper is also deposited on the photosensitive resin layer, a copper coating (for example, copper wiring) may be formed in a predetermined base film region by removing the photosensitive resin layer after the CVD of copper. it can.
[0023]
That is, the present inventors use trimethylvinylsilane-added hexafluoroacetyl acetonato copper as a copper source gas, 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.
[0024]
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.
[0025]
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. Subsequently, 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.
[0026]
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.
[0027]
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, Cu deposition under such conditions is performed on a hydrophilic undercoat film on which the source gas is adsorbed, and in the hydrophobic photosensitive resin layer in which the adsorption of the source gas is hindered, the Cu deposition is almost not. It can be seen that selective deposition that is not done can be performed.
[0028]
As described above, according to the present invention, the photosensitive resin layer is formed on the base film on the substrate, and the opening is formed in the copper film formation planned region by performing exposure and development treatment, and the bottom exposed from the opening. After the hydrophilic / hydrophobic difference is generated between the base film portion and the photosensitive resin layer, the CVD (copper source gas adsorption decomposition reaction) of copper at a low temperature such as 150 to 220 ° C. is performed. Copper can be selectively deposited on the hydrophilic base film region (the region where copper coating is to be formed). At this time, even if a small amount of copper is deposited on the photosensitive resin layer, the photosensitive resin layer is removed, so that a copper coating (for example, copper wiring) faithful to the opening pattern of the photosensitive resin layer is removed by so-called lift-off. ) Can 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.
[0029]
Further, by following exposure of the photosensitive resin layer exposed to a plasma of a mixed gas containing O ₂ gas or O ₂ gas, it is possible to completely remove the circle of the photosensitive resin layer at the opening after development. In such a state, a hydrophilic base film exposed from the opening of the photosensitive resin layer by performing CVD (adsorption decomposition reaction of copper source gas) of copper at a low temperature such as 150 to 220 ° C. Copper can be selectively deposited only in the portion (the area where the copper film is to be formed), and after removing the photosensitive resin layer after the CVD of copper, a copper film that is faithful to the shape of the opening is formed in a predetermined base film area. It can be formed selectively.
[0030]
【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.
[0031]
(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 with a resist pattern (not shown) masked.
[0032]
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.
[0033]
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 a low pressure CVD method. 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.
[0034]
Next, a positive cresol novolak resist is applied on the silicon nitride film 28 including the contact holes 29 by spin coating, dried, exposed, and developed, as shown in FIG. A resist layer 31 having a thickness of 1.0 μm having an opening 30 in a region corresponding to the contact hole 29 and its peripheral portion was formed. 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 180 ° C. and a source gas pressure of 1 torr, FIG. As shown, Cu was mainly deposited in the contact hole 29 exposed from the opening 30 of the resist layer 31 and on the silicon nitride film 28 in the vicinity thereof to form the source electrode wiring 32 and the drain electrode wiring 33. At this time, a slight amount of granular Cu 34 was also deposited on the resist layer 31. Subsequently, an array substrate having TFTs as shown in FIG. 4G was manufactured by removing the resist layer 31 having the granular Cu 34 deposited on the surface thereof with an organic solvent.
[0035]
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.
[0036]
(Example 2)
After a contact hole 29 is opened in the silicon nitride film 28 by the same method as in the first embodiment, the silicon nitride film 28 including the contact hole 29 is spin-coated on the silicon nitride film 28 including the contact hole 29 as shown in FIG. A positive cresol novolak resist was applied and dried to form a resist layer 31 having a thickness of 1.0 μm.
[0037]
Next, the resist layer was exposed and developed to form an opening 30 in the region of the resist layer 31 corresponding to the contact hole 29 and its peripheral portion. Subsequently, it was exposed to plasma of a mixed gas of CF ₄ and O ₂ having an O ₂ content of 95% by volume. Thereafter, selective CVD is performed under the conditions of a substrate temperature of 180 ° C. and a source gas pressure of 1 torr using a trimethylvinylsilane-added hexafluoroacetylacetonate copper which is a copper source gas. As shown in the figure, Cu was deposited only in the contact hole 29 exposed from the opening 30 of the resist layer 31 and on the silicon nitride film 28 in the vicinity thereof to form the source electrode wiring 32 and the drain electrode wiring 33. Subsequently, the resist layer 31 was removed with an organic solvent to manufacture an array substrate having TFTs shown in FIG.
[0038]
【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.
[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,
30 ... opening,
31 ... resist layer,
32 ... source electrode wiring,
33: Drain electrode wiring.

Claims (5)

Forming a thin film having a hydrophobic surface on the surface of the hydrophilic base film on the substrate;
Forming an opening in the copper film formation planned region of the thin film to expose the base film;
Performing CVD of copper at a substrate temperature of 220 ° C. or lower, and depositing a copper film on the underlying film mainly exposed from the opening of the thin film;
A method for selectively forming a copper film, comprising the step of removing the thin film.   The thin film having a hydrophobic surface is a photosensitive resin layer, and the opening of the region where the copper coating is to be formed is formed by exposing and developing the photosensitive resin layer. The method for selectively forming a copper coating according to 1. The exposure of the photosensitive resin layer, the method for selectively forming a copper film of claim 2, wherein the exposure to the plasma of the mixed gas after development including O ₂ gas or O ₂ gas. 3. The method for selectively forming a copper film according to claim 2, wherein the photosensitive resin layer is exposed to at least one of ozone gas and ultraviolet light after exposure and development . Forming a thin film having a hydrophobic surface on the surface of the hydrophilic base film on the substrate;
Forming an opening in the copper film formation planned region of the thin film to expose the base film;
Performing copper CVD at a substrate temperature of 220 ° C. or lower, and depositing copper wiring on a base film mainly exposed from the opening of the thin film;
A method for manufacturing a semiconductor device, comprising: removing the thin film.

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