US20120298518A1

US20120298518A1 - Electroplating apparatus and method

Info

Publication number: US20120298518A1
Application number: US13/182,632
Authority: US
Inventors: Seung Ki Joo
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-05-26
Filing date: 2011-07-14
Publication date: 2012-11-29
Also published as: KR20120132266A; KR101283009B1

Abstract

Provided is an electroplating apparatus including: a copper electrode plate that is disposed with a gap from an upper surface of an insulating substrate on which seed electrodes are formed; a driving unit that makes the copper electrode plate move along a rectilinear line; a power supply that applies electric current between the copper electrode plate and each of the seed electrodes; and spacers that are provided on the lower surface of the copper electrode plate to thereby make an electrolyte stay by surface tension between the copper electrode plate and the insulating substrate, and that maintains the gap between the copper electrode plate and the insulating substrate so that the electrolyte may move together with the copper electrode plate. Accordingly, a uniform copper film can be formed on the surface of a large substrate.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2011-0050343, filed on May 26, 2011; and Korean Patent Application No. 10-2011-0065375, filed on Jul. 1, 2011, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an apparatus for forming a metal thin film on a substrate, and more particularly, to an electroplating apparatus and method that can uniformly form a metal thin film on a large substrate.
2. Description of the Related Art
In general, various kinds of metal and metal alloys such as aluminum (Al), molybdenum (Mo), and molybdenum-tungsten (MoW) are used as a gate electrode constituting a bottom gate of a thin film transistor (hereinafter referred to TFT). The reason why the aluminum (Al), molybdenum (Mo), molybdenum-tungsten (MoW), etc., are used as a material of the gate electrode is because for example aluminum oxide (Al2O3) can be used as a gate insulation film to thereby make it easy to make the gate insulation film.
However, in the case that aluminum is used as a gate electrode material to implement a large display, in recent years, a resistance value of a gate line (GL) that is mutually connected with a gate electrode and is simultaneously formed with the gate electrode and that is simultaneously formed together with the gate electrode in general, or a data line (DL) that is orthogonally formed with respect to the gate line (GL) and is connected to a source region, is greatly increased in proportion to the dimension of a display. As a result, a gate signal and a data signal have been delayed and distorted.
In particular, in the case of an ultra-large flat-panel display whose one side is one meter or more long, a total length of wires increases exponentially. Accordingly, it is essential to use copper with low resistance as a material of wires. Since it is difficult to lower resistance of a gate wire of a thin film transistor (TFT) in comparison with that of a data wire, among the gate and data wires, it is required to use copper as the gate wire.
Conventional gate electrode materials are metal materials including copper (Cu) whose resistance is smaller than that of aluminum (Al). However, an appropriate etching solution that is used for etching a copper film in order to form the gate electrode and gate line has not been developed. Further, there is a problem that an etching process for etching the copper film produces heavy metals causing an environmental pollution.
Unlike the above-described metal and metal alloys, copper does not constitutes fluoride or chloride, there is a problem that copper is not well etched. In addition, in the case that copper is piled up with a thick thickness in order to reduce resistance, there is a problem that it takes 3-4 hours or longer as a processing time.
In addition, in the case that copper is used as the gate electrode in a large display, respective copper wires of one micrometer or more thick are required in order to make resistance of the copper wires sufficiently small. However, it takes long time to form a copper thick film of such a thickness. Further, in the case that a gate electrode structure of a thick film is employed, a gate insulation film that is directly formed on the upper portion of a gate electrode by a well-known process may cause a step coverage problem.
In order to these problems, a thick insulation film of 2 micrometers or so is deposited and patterned, to thereby form a trench structure. The trench structure is filled with copper by an electrodeposition process, to thus form wires. Here, a special technology is needed to selectively electrodeposite copper in the trench structure. According to the conventional electrodeposition technology, it is not possible to form a uniform copper film on the entire surface of the substrate because of high resistance in the case of a large area display. Besides, there is a need to use a large container accommodating a liquid electrolyte.
Meanwhile, a conventional technology of manufacturing an array substrate using copper as a gate electrode is disclosed in Korean Patent Laid-open Publication No. 10-2006-115522.
In the Korean Patent Laid-open Publication No. 10-2006-115522, signal wires and a thin film transistor are manufactured using an electroless plating method or an electroplating method whose deposition temperature is low, considering manufacturing temperature and stress act as big constraints in the case that the array substrate using copper as a gate electrode, in comparison with a case that a glass substrates is used at the time of production of signal wires such as gate lines and data lines and a thin film transistor in order to implement a flexible display device, to thereby prevent a flexible substrate from being bent or signal line layers from being cracked, and simultaneously to thereby promote a quality of display to be improved.
To this end, the Korean Patent Laid-open Publication No. 10-2006-115522 discloses that a first electrode layer made of nickel or molybdenum, a second electrode layer made of copper, and first and second line layers for use in gate lines and data lines are formed by the electroless plating method, to thereby form an electroplating seed layer, and then source and drain regions, and a third electrode layer and a third line layer for use in gate lines and data lines are formed by the electroplating method using the electroplating seed layer.
However, the method of forming the copper gate electrode and wires of the Korean Patent Laid-open Publication No. 10-2006-115522 includes a process of patterning first and second electrode layers so as to form the copper gate electrode and wires using the electroplating method, after having formed the first electrode layer for enhanced adhesion and the second electrode layer made of copper on the entire surface of the substrate by the electroless plating. As a result, the Korean Patent Laid-open Publication No. 10-2006-115522 has the same problem as that of the conventional art at the time of etching the copper metal layer.
In addition, the technology disclosed in the Korean Patent Laid-open Publication No. 10-2006-115522 may cause a step coverage problem in a subsequent process of forming the gate electrode as a thick film of one micrometer or more thick, and does not present any related solutions.
Moreover, when source and drain regions are formed in alignment with a gate electrode in the conventional art, a mask for shielding ion implantation is formed on the upper portion of the gate electrode by using a separate exposure mask and then an ion implantation process is executed. Accordingly, an alignment error of 2 to 4 micrometers may be caused. Further, such an alignment error cannot be equally distributed to both ends of a channel region and leans toward one end of the channel region, to thereby become a factor of aggravating an electrical performance of the thin film transistor (TFT).
Meanwhile, a copper electroplating process is a conventional technology, but has no problem when it is used in general with a traditional approach. However, in the case of a large substrate whose one side is two or more meters long, a problem such as a voltage drop may be caused. Accordingly, it is difficult to electroplate a metal film of uniform thickness on the large substrate.
In addition, the copper electroplating process requires that a container containing an electrolyte should be large in itself, and a huge amount of the electrolyte should be needed, to accordingly cause many industrial problems.
Moreover, when the electroplating is utilized in a semiconductor manufacturing process, a problem bigger than that of maintaining uniformity in thickness of an electrodeposited metal film is regulation of grain size. When grains are ripened as an example, the surface of the electrodeposited metal film becomes coarse. Thus, since surface roughness of a few micrometers may also cause a big problem in the semiconductor manufacturing process, grain size should become a micrometer level or less unlike typical applicable cases.
A conventional typical wet copper plating system is configured as shown in FIG. 1. In FIG. 1, a plate-shaped copper (Cu) electrode 160 and a substrate 130 on which a metal seed layer 150, that is, a metal electrode 150 is formed in which copper plating is performed on the metal electrode 150 are dipped in an electroplating tub 100 that is filled with a CuSO₄electrolyte 110. Then, the metal electrode 150 is established as a cathode and the copper electrode 160 is established as an anode. Then, electric power is supplied from a power supply 140 in order to execute an electroplating process. Accordingly, a copper plated layer 170 is electrodeposited on the metal electrode 150.
Meanwhile, in the case of using the conventional typical wet copper plating system that dips a large-area substrate whose electrodeposition area is wide like a large display substrate whose one side is two meters or more long, in order to perform a copper plating process, the metal electrode 150 that is used as the cathode may cause a big difference in electric current densities between a portion “a” close to a power supply and a portion “b” far from the power supply, due to a voltage drop across resistance values of the portions “a” and “b.”
During performing the wet copper plating process, an electrodeposition rate is proportional to an electric current density. Here, the following formula is established.
Electric current density=Electric current/Electrodeposition area
Thus, since copper (Cu) nucleation occurs rapidly at a portion of a high current density, grain size is small as illustrated as the portion “a” of FIG. 2. However, since nucleation does not occur well at a portion of a low current density, a phenomenon that grain size becomes large occurs as the portion “b” of FIG. 2.
In the electroplating process, grain size is dependent upon a voltage applied across both a cathode and an anode, an electric current that flows between the cathode and the anode, an electrolyte concentration, a distance between the cathode and the anode. Thus, in the case of using a large tub that can contain a large display substrate, it is extremely difficult to control such many variables.
As a result, in the case that copper plating is performed on a large-area substrate by using the conventional wet plating method employing the conventional dipping process, grain of a plated copper film is not formed into a uniform size.

SUMMARY OF THE INVENTION

To solve the above conventional problems or defects, it is an object of the present invention to provide an electroplating apparatus and method that can uniformly form a metal thin film on a large substrate.
In addition, it is another object of the present invention to provide an electroplating apparatus and method that has no need to provide a large vessel containing an electrolyte, and that enables copper to be electrodeposited uniformly.
In addition, it is still another object of the present invention to provide an electroplating apparatus and method, in which a copper gate is selectively formed in an insulation layer having a trench structure, to thereby eliminate a step coverage problem at the time of forming a gate insulation film, without passing through a separate planarization process.
Furthermore, it is yet another object of the present invention to provide an electroplating apparatus and method, in which copper is formed as a gate electrode and simultaneously an amorphous silicon film is crystallized to form a transparent polysilicon layer, to thereby make it possible to perform a strict control of a channel region by back exposure without using a separate exposure mask and automatically align a source region and a drain region with respect to a gate.
To accomplish the above and other objects of the present invention, according to an aspect of the present invention, there is provided an electroplating apparatus comprising:
a copper electrode plate that is disposed with a gap from an upper surface of an insulating substrate on which seed electrodes are formed;
a driving unit that makes the copper electrode plate move along a rectilinear line;
a power supply that applies electric current between the copper electrode plate and each of the seed electrodes; and
spacers that are provided on the lower surface of the copper electrode plate to thereby make an electrolyte stay by surface tension between the copper electrode plate and the insulating substrate, and that maintains the gap between the copper electrode plate and the insulating substrate so that the electrolyte may move together with the copper electrode plate.
Preferably but not necessarily, the insulating substrate is formed of a hydrophobic material, to thus make the electrolyte stay by surface tension between the copper electrode plate and the insulating substrate.
Preferably but not necessarily, the driving unit comprises:
a driving motor that is actuated according to a signal applied from a control unit;
a pinion gear that is fixed on a driving shaft of the driving motor; and
a rack gear that is gear-engaged with the pinion gear and is fixed to the copper electrode plate.
According to another aspect of the present invention, there is also provided an electroplating apparatus comprising:
a copper electrode plate that is disposed with a gap from an upper surface of an insulating substrate on which seed electrodes are formed;
a pushing plate that is disposed at the rear side of the copper electrode plate to thus push an electrolyte toward the copper electrode plate;
a driving unit that makes the copper electrode plate and the pushing plate move along a rectilinear line;
a power supply that applies electric current between the copper electrode plate and each of the seed electrodes; and
spacers that are provided on the lower surface of the copper electrode plate to maintain the gap between the copper electrode plate and the insulating substrate.
According to still another aspect of the present invention, there is still also provided an electroplating apparatus comprising:
a copper electrode plate that is disposed with a gap from an upper surface of an insulating substrate on which seed electrodes are formed;
an electrolyte supplier that is disposed at the front side of the copper electrode plate to thus supply an electrolyte on the surface of the insulating substrate;
an electrolyte remover that is disposed at the rear side of the copper electrode plate to thus remove the electrolyte from the copper electrode plate;
a power supply that applies electric current between the copper electrode plate and each of the seed electrodes; and
spacers that are provided on the lower surface of the copper electrode plate to maintain the gap between the copper electrode plate and the insulating substrate; and
a driving unit that makes the copper electrode plate, the electrolyte supplier and the electrolyte remover move along a rectilinear line.
Preferably but not necessarily, the electrolyte supplier comprises:
a nozzle body that is connected with the driving unit to thus move along a rectilinear line and through which the electrolyte enters; and
a plurality of supply nozzles that are arranged on the lower portion of the nozzle body to thus supply the electrolyte for the insulating substrate.
Preferably but not necessarily, the electrolyte remover is formed of an adsorption member that adsorbs the electrolyte.
According to yet another aspect of the present invention, there is yet also provided an electroplating method comprising the steps of:
forming seed electrodes on an insulating substrate;
making a copper electrode plate disposed with a gap from an upper surface of the insulating substrate, to then make an electrolyte placed between the copper electrode plate and the insulating substrate;
applying electric current between the copper electrode plate and each of the seed electrodes, to thus form a copper film on the surface of each of the seed electrodes; and
making the copper electrode plate move in a rectilinear line to thus sequentially form a copper film on the surface of each of the seed electrodes.
Preferably but not necessarily, in the case that the insulating substrate is hydrophobic, the electrolyte stays by surface tension between the copper electrode plate and the insulating substrate, and the copper electrode plate moves together with the electrolyte.
Preferably but not necessarily, the electroplating method further comprises the step of making a pushing plate disposed at the rear side of the copper electrode plate, to thus push the electrolyte toward the copper electrode plate, in the case that the insulating substrate is hydrophilic.
Preferably but not necessarily, the electroplating method further comprises the steps of supplying the electrolyte from the front side of the copper electrode plate, and removing the electrolyte at the rear side of the copper electrode plate, in the case that the insulating substrate is hydrophilic.

Advantageous Effects

As described above, an electroplating apparatus and method according to the present invention can form a metal thin film uniformly on a large substrate.
In addition, when a bottom gate is formed of copper with a low resistance value that is appropriate for a large display by an electroplating method, an electrolyte is coated on seed layers formed on a substrate so as to be supported by surface tension and a copper plate that is an anode is made to move along the seed layers, to thus electrodeposite copper wires thereon.
In addition, the electroplating apparatus and method according to the present invention does not require for a large device that contains an electrolyte and enables copper to be electrodeposited uniformly.
Therefore, in the case of an electroplating apparatus and method according to the present invention, copper with a low resistance value that is suitable for a large display is selectively formed quickly into a thickness usable for a bottom gate according to an electroplating method, to thereby minimize a processing time and simultaneously omit a copper etching process.
In addition, the present invention can solve a step coverage problem without passing through a planarization process by selectively forming a trench type copper bottom gate structure using copper that is used as a gate electrode.
Furthermore, since the present invention uses copper for a gate electrode, a source region and a drain region can be automatically aligned with respect to a gate by back exposure without using a separate mask, to thereby minimize an alignment error.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configurational diagram showing a conventional wet electroplating apparatus.

FIG. 2 shows photographs showing that grain size varies according to local areas when copper is electrodeposited on a large substrate according to the conventional art.

FIG. 3 is a perspective view showing an electroplating apparatus according to an embodiment of the present invention.

FIG. 4 is a perspective view showing an electroplating apparatus according to another embodiment of the present invention.

FIG. 5 is a perspective view showing an electroplating apparatus according to still another embodiment of the present invention.

FIG. 6 is a plan view illustrating an array substrate of a liquid crystal display device according to the present invention.

FIGS. 7 through 22 are cross-sectional views illustrating a process of manufacturing a trench type copper bottom gate thin film transistor, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The above and/or other objects and/or advantages of the present invention will become more apparent by the following description.
Hereinbelow, an electroplating apparatus and method according to preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings FIGS. 3 through 22. Here, components shown in the drawings can be exaggerated in size or shape for illustrative clarity and convenience. In addition, terms that are specifically defined by considering configuration and function of the present invention may vary depending on a user's or operator's intention or practice. The definition of these terms should be made based on contents that are described through this disclosure.
FIG. 3 is a perspective view showing an electroplating apparatus according to a first embodiment of the present invention.
Referring to FIG. 3, the electroplating apparatus according to the first embodiment according to the present invention includes: a copper electrode plate 50 that is disposed so as to move along a rectilinear line on an upper surface of an insulating substrate 11 on which seed electrodes 12 are formed; a driving unit 60 that makes the copper electrode plate 50 move reciprocally along a rectilinear line; and a power supply 54 that applies electric current between the copper electrode plate 50 and each of the seed electrodes 12.
A method of forming the seed electrodes 12 on the insulating substrate 11 will follow in detail.
In the case that the insulating substrate 11 is formed of a hydrophobic material, an electrolyte 70 does not spread but forms on the surface of the insulating substrate 11. As a result, the electrolyte 70 stay between the copper electrode plate 50 and the insulating substrate 11 by surface tension that causes electrolyte 70 to form on the surface of the insulating substrate 11. When the copper electrode plate 50 moves, the electrolyte 70 also moves together with the copper electrode plate 50.
Spacers 52 are provided in contact with the surface of the insulating substrate 11 at both ends of the lower surface of the copper electrode plate 50, to thus consistently maintain a gap between the copper electrode plate 50 and the insulating substrate 11.
The gap formed between the copper electrode plate 50 and the insulating substrate 11 makes the electrolyte 70 form surface tension between the copper electrode plate 50 and the insulating substrate 11, so that the electrolyte 70 may move together with the copper electrode plate 50.
A driving unit 60 includes: a driving motor 62; a pinion gear 64 that is fixed on a driving shaft of the driving motor 62; a rack gear 66 that is fixed to an upper surface of the copper electrode plate 50 and is gear-engaged with the pinion gear 64; and a control unit 68 that controls the driving motor 62. In other words, when the driving motor 62 is actuated depending on a signal from the control unit 68, the driving unit 60 performs a scanning action that the copper electrode plate 50 moves along a rectilinear line by the pinion gear 64 and the rack gear 66.
The driving unit 60 may employ any structure that the copper electrode plate can move reciprocally along a rectilinear line such as a cylinder type, a solenoid type, and a screw type, other than the above-described rack gear and pinion gear structure.
The function of the electroplating apparatus having the above-described configuration according to the first embodiment of the present invention will follow.
The copper electrode plate 50 is aligned on an upper surface of the insulating substrate 11 on which the seed electrodes 12 are formed. Then, the electrolyte 70 is placed between the copper electrode plate 50 and the insulating substrate 11. Here, the electrolyte 70 will stay by surface tension between the copper electrode plate 50 and the insulating substrate 11.
Under these conditions, when the power supply 54 applies electric current between each of the seed electrodes 12 and the copper electrode plate 50, metal ions of the copper electrode plate 50 are electrodeposited on the respective surfaces of the seed electrodes 12 through the electrolyte 70, to thereby form a copper film 37. In addition, when electric power is applied to the driving motor 62 by the control unit 68, the pinion gear 64 is made to rotate, and the rack gear 66 that is gear-engaged with the pinion gear 64 is made to move along a rectilinear line. Thus, the copper electrode plate 50 that is fixed to the rack gear 66 is made to perform a linear movement.
Then, the electrolyte 70 moves together with the copper electrode plate 50 by surface tension while the copper film 37 is sequentially formed on the respective surfaces of the seed electrodes 12.
As described above, in the case of the electroplating apparatus according to the first embodiment of the present invention, when the copper plating device electrode plate 50 moves along the rectilinear line, the copper film 37 is sequentially formed on the respective surfaces of the seed electrodes 12. Accordingly, thickness of the copper film can be uniformly formed and fine grain particles can be guaranteed, in comparison with a case that the whole substrate is plated all at a time by a dipping method.
When the copper plating employing the scanning method is executed once, copper (Cu) grain that is relatively uniform in size can be produced with 2000-3000 Å in thickness on a large-sized substrate. Here, the electrodeposited copper film of 2000-3000 Å thick also provides an effect of lowering resistance of the metal electrode that is the cathode.
Therefore, the present invention can employ two-step processes including a first-step process of forming the copper film of 2000-3000 Å thick by the scanning method and a second-step process of forming the copper film of 1-2 micrometers thick as desired by dipping the substrate into the electrolyte and electrodepositing the copper film on the substrate. The case of forming the copper film using the two-step processes is more advantageous than a case of forming the copper film using the one-step process, in view of uniformity of the copper film.
In addition, in the present invention, a scan rate and an electric current density may significantly influence upon a copper (Cu) electrodeposition speed, a copper (Cu) grain size, and an electrodeposition shape. That is, when the electric current density becomes high above a certain value, electrodeposition is performed in a dendroid form. In this case, even if the scan rate becomes a certain value or less, electrodeposition is performed in a dendroid form. This is because a strong electric field is applied between the copper electrode plate 50 and the insulating substrate 11 since the copper electrode plate 50 and the insulating substrate 11 are very closely spaced with a gap of 1 mm or so from each other.
In addition, if the scan rate is too slow, an electrodeposited copper film becomes thick and thus resistance of the metal electrode becomes lowered. Accordingly, a phenomenon of instantaneously increasing the electric current density appears. Thus, the present invention can form the copper film at the electric current density and the scan rate that do not cause the dendroid growth to occur, to thereby obtain a uniform copper film. To this end, a scanning operation is executed first at a high electric current density, to thus make nucleation, and then the scanning operation is repeated at a low electric current density, to thereby avoid a dendroid phenomenon and fill copper into a trench.
In addition, if the electric current density becomes a certain value or less, or the scan speed is too fast, it is difficult to attain nucleation. Accordingly, grain size becomes large and surface of the copper film becomes rough.
In the present invention, all metals including copper and metal alloys thereof can be used as electrodeposition metal.
Scanning can be repeated as desired while changing voltage, current, scan rate, etc.
As described above, it is possible to form a thin copper film by a single scan, and perform an electroplating in an electrolyte to thus form a uniform copper film or fill copper into a trench or hole.
FIG. 4 is a perspective view showing an electroplating apparatus according to a second embodiment of the present invention.
Referring to FIG. 4, the electroplating apparatus according to the second embodiment of the present invention includes: a copper electrode plate 50 that is disposed so as to move along a rectilinear line on an upper surface of an insulating substrate 11 on which seed electrodes 12 are formed; a pushing plate 56 that is disposed at the rear side of the copper electrode plate 50 to thus push an electrolyte 70 that is placed at the rear side of the copper electrode plate 50 toward the copper electrode plate 50; a driving unit 60 that makes the copper electrode plate 50 and the pushing plate 56 move along a rectilinear line; and a power supply 54 that is connected between the copper electrode plate 50 and each of the seed electrodes 12 and thus applies electric current between the copper electrode plate 50 and each of the seed electrodes 12.
If the insulating substrate 11 is hydrophilic as a silicon oxide film, the electrolyte 70 is widely spread on the surface of the insulating substrate 11. Thus, the pushing plate 56 is made to push the electrolyte 70 so that the electrolyte 70 may be disposed at only a portion where the copper electrode plate 50 is placed.
Here, the pushing plate 56 is made of a material having an elasticity such as a rubber or silicone material, and is closely adhered to the surface of the insulating substrate 11 to then move forward. Then, the pushing plate 56 pushes the electrolyte 70 that has been spread on the surface of the insulating substrate 11 toward the copper electrode plate 50, to then remove the electrolyte 70 that remains at the rear side of the copper electrode plate 50.
Since the driving unit 60 and the power supply 54 of the second embodiment of the present invention are of the same configuration and function as those of the driving unit 60 and the power supply 54 of the first embodiment of the present invention, the detailed description thereof will be omitted.
The function of the electroplating apparatus having the above-described configuration according to the second embodiment of the present invention will follow.
The copper electrode plate 50 is aligned on an upper surface of the insulating substrate 11 on which the seed electrodes 12 are formed, in which spacers 52 are provided on the lower surface of the copper electrode plate 50 to maintain a gap between the copper electrode plate 50 and the insulating substrate 11. Then, the pushing plate 56 is aligned at the rear side of the copper electrode plate 50, so as to closely contact the surface of the insulating substrate 11. Then, the electrolyte 70 is placed between the copper electrode plate 50 and the insulating substrate 11. Here, the electrolyte 70 will stay by surface tension between the copper electrode plate 50 and the insulating substrate 11.
Under these conditions, when the power supply 54 applies electric current between each of the seed electrodes 12 and the copper electrode plate 50, a copper film 37 is electrodeposited on the respective surfaces of the seed electrodes 12 through the electrolyte 70. In addition, the driving unit 60 is driven by the control unit 68, to thus make the copper electrode plate 50 and the pushing plate 56 move along a rectilinear line. Then, the electrolyte 70 moves together with the copper electrode plate 50 by the pushing plate 56, while the copper film 37 is sequentially formed on the respective surfaces of the seed electrodes 12.
Here, the pushing plate 56 pushes the electrolyte 70 in the direction of the copper electrode plate 50, to thus remove the electrolyte 70 that exists in the rear side of the copper electrode plate 50, and make the electrolyte 70 placed on the bottom of the copper electrode plate 50. Accordingly, the copper film 37 is sequentially formed to thereby enable uniform electrodeposition.
FIG. 5 is a perspective view showing an electroplating apparatus according to a third embodiment of the present invention.
Referring to FIG. 5, the electroplating apparatus according to the third embodiment of the present invention includes: a copper electrode plate 50 that is disposed so as to move along a rectilinear line on an upper surface of an insulating substrate 11 on which seed electrodes 12 are formed; an electrolyte supplier 80 that is disposed at the front side of the copper electrode plate 50 to thus supply an electrolyte 70 on the surface of the insulating substrate 11; an electrolyte remover 90 that is disposed at the rear side of the copper electrode plate 50 to thus remove the electrolyte from the copper electrode plate 50; a driving unit 60 that makes the copper electrode plate 50, the electrolyte supplier 80 and the electrolyte remover 90 move along a rectilinear line; and a power supply that is connected between the copper electrode plate 50 and each of the seed electrodes 12, and applies electric current between the copper electrode plate 50 and each of the seed electrodes 12.
The insulating substrate 11 is formed of a hydrophilic material such as a silicon oxide film to thus make the electrolyte widely spread on the upper surface of the insulating substrate 11.
Thus, the electrolyte supplier 80 continuously supplies a certain amount of the electrolyte that is needed for the electroplating process to the copper electrode plate 50 is provided at the front side of the copper electrode plate 50. In addition, the electrolyte remover 90 that removes the electrolyte from the copper electrode plate 50 is provided at the rear side of the copper electrode plate 50.
The electrolyte supplier 80 includes: a nozzle body 82 that is connected with the rack gear 66 of the driving unit 60 and through which the electrolyte enters; and a plurality of supply nozzles 84 that are arranged at intervals on the lower portion of the nozzle body 82 to thus supply the electrolyte for the surface of the insulating substrate 11. In addition, the nozzle body 82 is connected with an electrolyte vessel and a supply hose, and a pump for pumping the electrolyte is provided in the electrolyte vessel.
Since the driving unit 60 and the power supply 54 of the third embodiment of the present invention are of the same configuration and function as those of the driving unit 60 and the power supply 54 of the first embodiment of the present invention, the detailed description thereof will be omitted. However, the rack gear 66 of the driving unit 60 is connected with the copper electrode plate 50, the electrolyte remover 90 and the electrolyte supply unit 80, to thereby make the three components of the copper electrode plate 50, the electrolyte remover 90 and the electrolyte supply unit 80 move straightforward all at a time.
Spacers 52 are provided on the lower surface of the copper electrode plate 50 to maintain the gap between the copper electrode plate 50 and the insulating substrate 11.
The electrolyte remover 90 removes the electrolyte that remains at the rear of the copper electrode plate 50 and includes: a case 92 whose lower portion is opened and upper portion is connected to the rack gear 66; and an adsorption member 94 that is contained in the case 92 and withdrawn through the opened lower portion of the case 92, to thereby adsorb the electrolyte.
Any material such as a sponge material that can adsorb a solution can be used as the adsorption member 94.
The electrolyte remover 90 includes: a suction nozzle that inhales an electrolyte and a vacuum pump that is connected with the suction nozzle to thus generate a suction force, other than the above-described adsorption structure. In other words, any structure that can remove the electrolyte remaining at the rear of the copper electrode plate can be applicable as the electrolyte remover.
The function of the electroplating apparatus having the above-described configuration according to the third embodiment of the present invention will follow.
The electrolyte remover 90, the copper electrode plate 50, and the electrolyte supplier 80 are sequentially aligned on the upper side of the insulating substrate 11 on which the seed electrodes 12 are formed.
Then, the electrolyte is supplied to the surface of the insulating substrate 11 through the electrolyte supplier 80, and then the power supply 54 supplies electric current between each of the seed electrodes 12 and the copper electrode plate 50. Accordingly, the copper film 37 is formed on the surface of the respective surfaces of the seed electrodes 12 through the electrolyte.
Then, the driving unit 60 is activated to make all of the electrolyte remover 90, the copper electrode plate 50 and the electrolyte supplier 80 move along a rectilinear line. In this case, while the copper electrode plate 50 moves, the copper film 37 is sequentially formed on the respective surfaces of the seed electrodes 12 in a scanning manner.
In addition, the electrolyte remover 90 removes the electrolyte that remains at the rear of the copper electrode plate 50, to thus prevent the copper film 37 from being electrodeposited at the rear side of the copper electrode plate 50.
FIG. 6 is a plan view illustrating an array substrate of a liquid crystal display device according to the present invention.
The liquid crystal display device includes an array substrate, a color filter substrate, and a liquid crystal layer formed between the array substrate and the color filter substrate, to thus display images thereon.
Referring to FIG. 6, the array substrate includes a number of gate lines (GLs) extended in a first direction (D1) and a number of data lines (DLs) extended in a second direction (D2) orthogonal to the first direction (D1). A number of pixel regions pixel electrodes 23 are defined by a number of the gate lines (GLs) that are formed simultaneously with a number of gate electrodes 14, or a number of the data lines (DLs) that are formed in a direction orthogonal to the number of the gate lines (GLs) and connected to a source electrode (S), respectively.
In addition, the array substrate includes a number of thin film transistors (TFTs) in which each thin film transistor (TFT) includes the gate electrode 14 branched from the gate line (GL), a source electrode (S) branched from the data line (DL), and a drain electrode (D) that is electrically connected in correspondence to the pixel electrode 23.
A process of manufacturing a thin film transistor (TFT) according to an embodiment of the present invention in which the thin film transistor (TFT) is included in the array substrate will be described with reference to FIGS. 7 through 22.
As shown in FIG. 7, a base metal film 120 that is formed of a first adhesive layer 120 a and a first electrode layer 120 b that are respectively formed of a conductor, for example, one of Ni, MoW, and Al through a sputtering or thin film deposition method is formed on a transparent insulating substrate 11, for example, a glass substrate.
Here, the first adhesive layer 120 a is formed into a thickness of 500 Å using nickel (Ni) for example, and the first electrode layer 120 b is formed into a thickness of 2000 Å using molybdenum-tungsten (MoW) for example.
Then, after having formed a photoresist although it is not shown in FIG. 8, the base metal film 120 is patterned using a gate mask, to thereby form a seed electrode 12 in correspondence to the gate electrode of a shape shown in FIG. 8.
By doing so, the seed electrode 12 is completely patterned. Upon completion of the seed electrode formation, for example, a 1.5 micrometer-thick insulating film 13 is deposited using silicon oxide or silicon nitride by a plasma enhanced chemical vapor deposition (PECVD) method as shown in FIG. 9.
Thereafter, a photoresist layer 15 is coated on top of the insulating film 13, as shown in FIG. 10. Then, a back exposure process is performed. Then, the photoresist layer 15 is exposed and developed by the back exposure without using a mask and then the negative type photoresist layer 15 that is not exposed by the seed electrode 12 is removed. As a result, the remaining etching mask 15 a is self-aligned as shown in FIG. 11, and a recess pattern is formed in correspondence to a gate pattern. Here, the insulation film 13 corresponding to the recess pattern corresponding to the gate pattern is reactive-ion-etched using hydrofluoride (HF) through the remaining etching mask 15 a. Then, as shown in FIG. 12, a trench type guide portion 16 is formed on the insulating substrate 11 and thus a trench type contact window is formed to make the upper portion of the seed electrode 12 exposed. Thereafter, the etching mask 15 a is removed.
Subsequently, copper is selectively electrodeposited with one or two micrometers thick on the exposed seed electrode 12 by an electroplating method using the trench type guide portion 16. As a result, copper is not electrodeposited on the trench type guide portion 16 but is electrodeposited on only the exposed upper trench of the exposed seed electrode 12 to thus selectively form a copper film 37 that is a gate electrode. In other words, the seed electrode 12 is set as a cathode and the copper is set as an anode, to then carry out an electroplating process. Accordingly, the copper film 37 is selectively formed.
In the present invention, the copper film 37 is formed in a scanning manner by the electroplating apparatus that are shown in FIGS. 3 to 5, as a copper plating process of forming the copper film 37 that is a copper gate electrode. In addition, in the case that thickness of the copper film 37 is thinner than a set value, the insulating substrate is dipped into the electrolyte tub and then the electroplating process is executed once again, to thereby form the a copper gate electrode 14. In addition, as shown in FIG. 13, in order to achieve planarization of the copper gate electrode 14, a planarization process such as a CMP (Chemo-Mechanical Polishing) process or a grinding process is executed considering that the copper gate electrode 14 is formed on the trench type guide portion 16, to thus execute planarization of the copper wires and the trench type guide portion 16.
Here, it is necessary to make a polishing unit move in a random direction on a large-area substrate, to thus planarize a copper gate that has been excessively charged or filled. In addition, the copper gate is polished with a fine abrasive agent without using a copper etching solution, to thus planarize the excessively charged or filled copper gate.
In this case, wires for gate lines (GLs) that are connected with the gate electrode 14 and are used to apply a gate signal to a thin film transistor (TFT) are preferably simultaneously formed. Here, data lines (DLs) that are connected to a source electrode (S) are also preferably formed in the same process and material as those of the gate lines (GLs).
Then, as shown in FIG. 14, a gate insulation film 17 is deposited by a thickness of 1000 Å on the gate electrode 14 and the trench type guide portion 16, by a PECVD (Plasma-Enhanced Chemical Vapor Deposition) method, for example. A silicon oxide film or silicon nitride film can be used as the gate insulation film 17.
Then, as shown in FIG. 15, an amorphous silicon layer 18 is deposited on the gate insulation film 17 by for example, a CVD (Chemical Vapor Deposition) method. In order to form a source region and a drain region during deposition of the amorphous silicon layer 18, an in-situ doping process can be simultaneously done.
In the case of forming the polysilicon thin film transistor (TFT), the in-situ doping process is not generally performed as will be described later. In the case that crystallization is performed using laser, a crystallization process is performed in front of or at the back of a protective oxide film. In the case of using a non-laser method, the crystallization process may vary depending on the applied method. In this embodiment, a metal induced lateral crystallization (MILC) method is applied for crystallization of the amorphous silicon layer as an example.
After the amorphous silicon layer 18 has been deposited, a photoresist mask 19 is formed as shown in FIG. 16, in order to form a metal induced film to induce crystallization of the amorphous silicon layer 18 by a lift-off method. Then, a nickel pattern layer 20 that is a metal induced film for the metal induced lateral crystallization MILC is formed on the photoresist mask 19 to then be removed as shown in FIG. 17. Here, Pd, Ti, Ag, Au, Al, Sn, Sb, Cu, Co, Cr, Mo, Tr, Ru, Rh, Cd, Pt, etc., may be used as materials of the crystallization metal induced film, in addition to nickel.
After the nickel pattern layer 20 has been formed, the amorphous silicon layer 18 is crystallized by a MILC (metal induced lateral crystallization) low-temperature heat treatment. Then, the nickel pattern layer 20 is removed to thereby form a crystallizing silicon layer 18 a as shown in FIG. 18.
Here, a technology of metal-induced-lateral-crystallizing the amorphous silicon layer by the MILC heat treatment is disclosed in Korean Patent Laid-open Publication No. 10-2009-42122 that was filed earlier by the same inventor as that of the present invention. Accordingly, the detailed description thereof will be omitted.
After the MILC heat treatment has been performed, the amorphous silicon layer has been completely crystallized, and then the polysilicon layer 18 a has been formed, a protective oxide film 21 is deposited with a thickness of 3000 Å on the polysilicon layer 18 a as shown in FIG. 19. In addition, a photoresist is coated on the protective oxide film 21 to thereby form a photoresist layer 22 as shown in FIG. 20.
Then, as shown in FIG. 20, the photoresist layer 22 is exposed and developed by back exposure without using a mask. Then, the unexposed photoresist layer 22 is removed. Then, when the protective oxide film 21 is etched using a remaining etching mask not shown, an ion implantation shielding mask 21 a is formed as shown in FIG. 21.
Using the ion implantation shielding mask 21 a, a source region and a drain region are formed by a dopant ion mass doping (IMD) process, and the ion mass doped dopant is activated by a heat treatment process.
Referring to FIG. 22, etching masks (not shown) are formed on the activated source electrode (S) and the activated drain electrode (D), to then form a channel layer (C) by an etching process. Then, a protective film 22 made of an inorganic insulation film is formed on the channel layer (C) as well as the source electrode (S) and the drain electrode (D). Then, a contact hole that exposes the drain electrode (D) through the protective film 22 is formed. Then, a pixel electrode 23 made of ITO (indium tin oxide) or IZO (indium zink oxide) is formed on the protective film 22, to accordingly complete manufacturing of an array substrate.
In the above description of the embodiment of the present invention, the case that the gate lines have been formed in the same manner and material as those of the gate electrode has been described as an example. However, the data lines that are connected to the source electrode can be formed in he same manner and material as those of the gate lines.
The above-described process of manufacturing the copper bottom gate thin film transistor may employ the other crystallization methods instead of the above-described MILC method, on the substrate where the planarized and thick gate copper wires are achieved. It is also possible to modify part of the TFT manufacturing process.
As described above, copper with a low resistance value that is suitable for a large display is formed into a thickness usable for a bottom gate according to an electroplating method, in the present invention, to thereby solve a step coverage problem without passing through a planarization process of copper that is used as a gate electrode.
In addition, since the present invention uses copper in a gate electrode, a source region and a drain region can be automatically aligned with respect to a gate by back exposure without using a separate mask, to thereby minimize an alignment error.
In the above embodiment of the present invention, the case that polysilicon has been used as an active area as an example, but it is possible to use amorphous silicon as the active area.
However, in this case, it is required to form a mask in the conventional well-known manner, instead of forming the ion implantation shielding mask using back exposure.
The present invention can be applied to a thin film transistor that is used for a display device such as an active-matrix liquid crystal display (AMLCD) or an active-matrix organic light emitting diode (AMOLED) display and a wiring method thereof.
As described above, the present invention has been described with respect to particularly preferred embodiments. However, the present invention is not limited to the above embodiments, and it is possible for one who has an ordinary skill in the art to make various modifications and variations, without departing off the spirit of the present invention. Thus, the protective scope of the present invention is not defined within the detailed description thereof but is defined by the claims to be described later and the technical spirit of the present invention.

Claims

1. An electroplating apparatus comprising:

a copper electrode plate that is disposed with a gap from an upper surface of an insulating substrate on which seed electrodes are formed;

a driving unit that makes the copper electrode plate move along a rectilinear line;

a power supply that applies electric current between the copper electrode plate and each of the seed electrodes; and

spacers that are provided on the lower surface of the copper electrode plate to thereby make an electrolyte stay by surface tension between the copper electrode plate and the insulating substrate, and that maintains the gap between the copper electrode plate and the insulating substrate so that the electrolyte may move together with the copper electrode plate.

2. The electroplating apparatus according to claim 1, wherein the insulating substrate is formed of a hydrophobic material, to thus make the electrolyte stay by surface tension between the copper electrode plate and the insulating substrate.

3. The electroplating apparatus according to claim 1, wherein the driving unit comprises:

a driving motor that is actuated according to a signal applied from a control unit;

a pinion gear that is fixed on a driving shaft of the driving motor; and

a rack gear that is gear-engaged with the pinion gear and is fixed to the copper electrode plate.

4. An electroplating apparatus comprising:

a pushing plate that is disposed at the rear side of the copper electrode plate to thus push an electrolyte toward the copper electrode plate;

a driving unit that makes the copper electrode plate and the pushing plate move along a rectilinear line;

spacers that are provided on the lower surface of the copper electrode plate to maintain the gap between the copper electrode plate and the insulating substrate.

5. The electroplating apparatus according to claim 4, wherein the insulating substrate is formed of a hydrophilic material to thus make the electrolyte widely spread on the upper surface of the insulating substrate.

6. The electroplating apparatus according to claim 4, wherein the pushing plate is formed of a rubber or silicon material so as to be closely adhered on the upper surface of the insulating substrate to thus push the electrolyte toward the copper electrode plate.

7. The electroplating apparatus according to claim 4, wherein the driving unit comprises:

a pinion gear that is fixed on a driving shaft of the driving motor; and

a rack gear that is gear-engaged with the pinion gear and is fixed to both the copper electrode plate and the pushing plate.

8. An electroplating apparatus comprising:

an electrolyte supplier that is disposed at the front side of the copper electrode plate to thus supply an electrolyte on the surface of the insulating substrate;

an electrolyte remover that is disposed at the rear side of the copper electrode plate to thus remove the electrolyte from the copper electrode plate;

spacers that are provided on the lower surface of the copper electrode plate to maintain the gap between the copper electrode plate and the insulating substrate; and

a driving unit that makes the copper electrode plate, the electrolyte supplier and the electrolyte remover move along a rectilinear line.

9. The electroplating apparatus according to claim 8, wherein the insulating substrate is formed of a hydrophilic material to thus make the electrolyte widely spread on the upper surface of the insulating substrate.

10. The electroplating apparatus according to claim 8, wherein the electrolyte supplier comprises:

a nozzle body that is connected with the driving unit to thus move along a rectilinear line and through which the electrolyte enters; and

a plurality of supply nozzles that are arranged on the lower portion of the nozzle body to thus supply the electrolyte for the insulating substrate.

11. The electroplating apparatus according to claim 8, wherein the electrolyte remover is formed of an adsorption member that adsorbs the electrolyte.

12. An electroplating method comprising the steps of:

forming seed electrodes on an insulating substrate;

making a copper electrode plate disposed with a gap from an upper surface of the insulating substrate, to then make an electrolyte placed between the copper electrode plate and the insulating substrate;

applying electric current between the copper electrode plate and each of the seed electrodes, to thus form a copper film on the surface of each of the seed electrodes; and

making the copper electrode plate move in a rectilinear line to thus sequentially form a copper film on the surface of each of the seed electrodes.

13. The electroplating method of claim 12, wherein in the case that the insulating substrate is hydrophobic, the electrolyte stays by surface tension between the copper electrode plate and the insulating substrate, and the copper electrode plate moves together with the electrolyte.

14. The electroplating method of claim 12, further comprising the step of making a pushing plate disposed at the rear side of the copper electrode plate, to thus push the electrolyte toward the copper electrode plate, in the case that the insulating substrate is hydrophilic.

15. The electroplating method of claim 12, further comprising the steps of supplying the electrolyte from the front side of the copper electrode plate, and removing the electrolyte at the rear side of the copper electrode plate.

16. The electroplating method of claim 12, further comprising the steps of dipping the insulating substrate into an electrolyte tub to then performing an electroplating once more if a copper film is formed on the surface of the insulating substrate.