JP2005064034A - Method for manufacturing tft, and method for manufacturing display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a TFT wherein productivity is high and cost is low. <P>SOLUTION: The method for manufacturing a TFT is characterized in that: a base film material is spread on the surface of a glass substrate 1 with ink jet system, and a base film 2 is formed; a polysilicon film formation process wherein an amorphous silicon film is formed on the surface of the base film 2 by plating or ordinary pressure chemical vapor deposition, the amorphous silicon film is made polycrystalline, and a polysilicon film 3 is formed; a mask pattern forming process wherein a first mask pattern 6 formed of graft polymer is formed on a surface of the polysilicon film 3; and a polysilicon island formation process wherein the polysilicon film 3 is etched by using the first mask pattern 6 and a polysilicon island 7 is formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a thin film transistor formed on a surface of a substrate and a method for manufacturing a display device.
[0002]
[Prior art]
In the method for manufacturing a thin film transistor, film formation and etching are repeatedly performed. Recently, plasma is often used for film formation and etching. When film formation or etching is performed using plasma, the surroundings must be in a high vacuum environment.
[0003]
In the case of forming a mask used for etching, a photoresist is applied to the surface of a film to be etched by spin coating, and the photoresist is irradiated with light through the photomask.
[0004]
[Problems to be solved by the invention]
However, when plasma is used for film formation or etching, it takes a long time to form a high vacuum environment, and there is a problem that productivity is lowered.
[0005]
Further, when spin coating is used for forming a mask, most of the photoresist is discarded, and there is a problem that the efficiency of use of the material is lowered.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inexpensive method for manufacturing a thin film transistor and a method for manufacturing a display device.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve the object, a thin film transistor manufacturing method and a display device manufacturing method of the present invention are configured as follows.
[0008]
(1) Applying a base film material to the surface of the substrate by an ink jet method to form a base film, and forming an amorphous silicon film on the surface of the base film by plating or atmospheric pressure chemical vapor deposition A polysilicon film forming step for forming a polysilicon film by polycrystallizing the amorphous silicon film; a mask pattern forming step for forming a mask pattern made of a graft polymer on the surface of the polysilicon film; and And a polysilicon island forming step of forming a polysilicon island by etching the polysilicon film using a mask pattern.
[0009]
The mask pattern forming step includes a mask material applying step for applying a mask material to the surface of the polysilicon film by an inkjet method, and a predetermined portion of the mask material is irradiated with ultraviolet rays, and the irradiated portion is graft-polymerized. And a removal step of forming the mask pattern on the surface of the polysilicon film by removing the graft material while leaving the graft-polymerized portion of the mask material.
[0010]
The mask pattern forming step includes a polymerization initiator application step of applying a polymerization initiator to a predetermined portion of the surface of the polysilicon film by an ink jet method, and an ink jet method on the surface of the polysilicon film from above the polymerization initiator. By applying a mask material, a graft polymerization step of graft-polymerizing a portion of the mask material in contact with the polymerization initiator, and removing the mask material leaving the graft-polymerized portion, thereby removing the poly And a removal step of forming the mask pattern on the surface of the silicon film.
[0011]
(2) In a method of manufacturing a thin film transistor using a polysilicon film as a semiconductor layer, a gate insulating film forming step of forming a gate insulating film by applying a gate insulating film material to the surface of the polysilicon film by an inkjet method; And a gate electrode forming step of forming a gate electrode on a predetermined portion of the surface of the gate insulating film by plating.
[0012]
In the gate electrode forming step, the gate electrode is formed by depositing and depositing a conductive material on the entire surface of the gate insulating film by plating and removing the conductive material while leaving the predetermined portion by etching. And an etching process.
[0013]
The gate electrode forming step includes a catalyst application step of applying a catalyst for promoting plating to a predetermined portion of the surface of the gate insulating film by an ink jet method, and the conductive material from above the catalyst on the surface of the gate insulating film. And a partial plating step of forming the gate electrode by depositing and depositing the conductive material only on the predetermined portion coated with the catalyst by utilizing the reaction between the conductive material and the catalyst. Features.
[0014]
(3) In a method of manufacturing a thin film transistor including a gate electrode on a surface of a polysilicon film with a gate insulating film interposed therebetween, an impurity implantation step for implanting impurities into the polysilicon film using the gate electrode as a mask, and the gate insulation A protective film forming step of forming a protective film for protecting the transistor by atmospheric pressure chemical vapor deposition on the surface of the film; and a mask pattern forming step of forming a mask pattern made of a graft polymer on the surface of the protective film; Etching the protective film and the gate insulating film using the mask pattern to form a contact hole communicating with the polysilicon film from the surface of the protective film, and at least the inside of the contact hole And a wiring forming process for forming wiring by plating. That.
[0015]
In the mask pattern forming step, a mask material applying step for applying a mask material on the surface of the protective film by an ink jet method, and a predetermined portion of the mask material is irradiated with ultraviolet rays to graft polymerize the irradiated portion. It is characterized by having a graft polymerization step and a removal step of forming the mask pattern on the surface of the protective film by removing the portion of the mask material that has been graft-polymerized.
[0016]
The mask pattern forming step includes a polymerization initiator coating step in which a polymerization initiator is applied to a predetermined portion of the surface of the protective film by an ink jet method, and a mask for masking from above the polymerization initiator by an ink jet method on the surface of the protective film. By applying a material, a graft polymerization step of graft-polymerizing a portion of the mask material that contacts the polymerization initiator, and removing the mask material leaving the graft-polymerized portion, the protective film And a removal step of forming the mask pattern on the surface of the substrate.
[0017]
The wiring forming step includes a whole surface plating step of attaching and depositing a wiring material on the entire surface of the protective film by plating, and removing the wiring material by etching leaving at least the inside of the contact hole. And an etching process for forming the film.
[0018]
The wiring formation step includes a catalyst application step of applying a catalyst for promoting plating by an ink jet method at least on the inner surface of the contact hole, and a conductive material is plated on the surface of the protective film from above the catalyst. And a partial plating step of forming the wiring by depositing and depositing the conductive material only on the inner surface of the contact hole coated with the catalyst using a reaction between the material and the catalyst. .
[0019]
(4) In a method for manufacturing a display device having a thin film transistor, a color resist forming step of forming a color resist by applying a color resist material to the surface of a protective film provided on the thin film transistor by an ink jet method, and the color resist And an ITO film forming step of forming an ITO film by applying an ITO film material to the surface of the film by an ink jet method.
[0020]
(5) Applying a base film material to the surface of the substrate by an ink jet method to form a base film, and forming an amorphous silicon film on the surface of the base film by plating or atmospheric pressure chemical vapor deposition A process of forming a polysilicon film by polycrystallizing the amorphous silicon film, applying a mask material to the surface of the polysilicon film by an ink jet method, and a predetermined portion of the mask material. After the graft polymerization, the mask material is removed except for the graft polymerized portion, thereby forming a first mask pattern made of a graft polymer on the surface of the polysilicon film. A polysilicon island is formed by etching the polysilicon film using the step and the first mask pattern. A polysilicon island forming step, a gate insulating film material is applied to the surface of the polysilicon island by an ink jet method to form a gate insulating film, and a predetermined portion of the surface of the gate insulating film is formed. A gate electrode forming step of forming a gate electrode by plating; an impurity injection step of implanting impurities into the polysilicon film using the gate electrode as a mask; and the gate by atmospheric pressure chemical vapor deposition on the surface of the gate insulating film. A protective film forming step for forming a protective film for protecting the electrode; and a mask material is applied to the surface of the protective film by an ink jet method, and a predetermined portion of the mask material is graft-polymerized, and then the mask material is used. A second mask pattern made of a graft polymer is formed on the surface of the protective film by removing the grafted portion of the material. A second mask pattern forming step of forming a mask, and etching the protective film and the gate insulating film using the second mask pattern, thereby forming a contact hole communicating with the polysilicon film from the surface of the protective film. A contact hole forming step for forming, a wiring forming step for forming a wiring by plating at least inside the contact hole, and a color resist material formed by applying a color resist material to the surface of the protective film by an ink jet method. It comprises a forming step and an ITO film forming step of forming an ITO film by applying an ITO film material to the surface of the color resist by an ink jet method.
[0021]
(6) In the method of manufacturing a thin film transistor in which a thin film transistor is formed by repeatedly performing film formation and etching on the surface of the substrate, a high vacuum environment is not used when performing the film formation and etching.
[0022]
(7) In the method for manufacturing a thin film transistor, in which the thin film transistor is formed by repeatedly forming and etching on the surface of the substrate, the film forming and etching are performed under normal pressure.
[0023]
(8) In a method of manufacturing a thin film transistor having a step of etching the film using a mask formed on the surface of the film, a spin coating is applied to a liquid that is a material of the mask when the mask is formed on the surface of the film. It is characterized by being painted using a method other than
[0024]
(9) In the method of manufacturing a thin film transistor having a mask pattern forming step of forming an etching mask pattern on the surface of the film, the mask pattern forming step includes a mask material in which a mask material is applied to the surface of the film by an inkjet method. A material coating step, a graft polymerization step of graft polymerizing a predetermined portion of the mask material, and a removal step of forming the mask pattern by removing the mask material while leaving the graft polymerized portion. It is characterized by.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0026]
1 (a) to 1 (h), 2 (a) to 2 (h), and 3 (a) to 3 (d) show the thin film transistor according to the first embodiment of the present invention. It is process drawing which shows a manufacturing process.
[0027]
First, a glass substrate 1 is prepared as shown in FIG.
[0028]
Next, as shown in FIG. 1B, a liquid base film material is applied to the entire surface of the glass substrate 1 by an ink jet method, and the base film material is heated and cured by a lamp. As a result, the base film 2 is formed on the entire surface of the glass substrate 1.
Note that silicon nitride or silicon oxide is used as the material of the base film 2.
[0029]
Next, as shown in FIG. 1C, an amorphous silicon film is formed on the entire surface of the base film 2 by plating or atmospheric pressure chemical vapor deposition, and this amorphous silicon film is polycrystallized by lamp annealing. As a result, a polysilicon film 3 is formed on the surface of the base film 2.
[0030]
Next, as shown in FIG. 1D, a liquid first mask material 4 is applied to the entire surface of the polysilicon film 3 by an ink jet method. As the material of the first mask material 4, as will be described later, an organic material having a property of being graft-polymerized by irradiation with ultraviolet rays, that is, a graft polymerization material is used.
[0031]
Next, as shown in FIG.1 (e), the irradiation part is graft-polymerized by irradiating the predetermined part of the 1st mask material 4 with an ultraviolet-ray. As a result, the portion of the first mask material 4 irradiated with the ultraviolet light becomes a solid graft polymer 5.
[0032]
Next, as shown in FIG. 1 (f), the first mask material 4 is removed leaving the graft polymer 5, that is, the portion irradiated with ultraviolet rays. As a result, a first mask pattern 6 made of a graft polymer is formed on the surface of the polysilicon film 3.
[0033]
Next, as shown in FIG. 1G, the polysilicon film 3 is wet etched using the first mask pattern 6 to form a polysilicon island 7 on the surface of the base film 2. When this polysilicon island 7 is formed, the first mask pattern 6 is removed from the surface of the polysilicon island 7 as shown in FIG.
[0034]
Next, as shown in FIG. 2A, a liquid gate insulating film material is applied to the surface of the base film 2 so as to cover the polysilicon island 7 by an ink jet method, and this gate insulating film material is applied by a lamp. Heat cure. As a result, a gate insulating film 8 covering the polysilicon island 7 is formed on the surface side of the base film 2.
[0035]
Next, as shown in FIG. 2B, a catalyst 32 for promoting plating is applied to a predetermined portion of the surface of the gate insulating film 8 by an ink jet method. Then, the gate insulating film 8 is immersed in an electric field solution containing the gate electrode material together with the glass substrate 1 so that the electrode material is attached and deposited only on the portion of the gate insulating film 8 where the catalyst 32 is applied. As a result, a gate electrode 10 is formed on a predetermined portion of the surface of the gate insulating film 8 as shown in FIG. As a material for the gate electrode 10, nickel, copper, or the like is used.
[0036]
A gate electrode 10 is formed on a predetermined portion of the surface of the gate insulating film 8 by depositing and depositing a conductive material such as nickel or copper by plating on the entire surface of the gate insulating film 8 and then wet-etching the conductive material. May be.
[0037]
Next, as shown in FIG. 2D, impurities are implanted into the polysilicon island 7 using the gate electrode 10 as a mask. The polysilicon island 7 is heated by a lamp to activate the implanted impurities. As a result, a source region 7 a and a drain region 7 b are formed on the polysilicon island 7. Further, dangling bonds of silicon atoms constituting the polysilicon island 7 are terminated with hydrogen atoms.
[0038]
Next, as shown in FIG. 2E, a protective film 11 is formed on the surface of the gate insulating film 8 so as to cover the gate electrode 10 by atmospheric pressure chemical vapor deposition. As a material for the protective film 11, silicon nitride or the like is used.
[0039]
Next, as shown in FIG. 2F, a liquid second mask material 12 is applied to the entire surface of the protective film 11 by an ink jet method. As the material of the second mask material 12, an organic material having the same properties as the first mask material 4 described above, that is, a graft polymerization material is used.
[0040]
Next, as shown in FIG. 2 (g), a predetermined portion of the second mask material 12 is irradiated with ultraviolet rays, and the irradiated portion is graft-polymerized. As a result, the portion of the second mask material 12 irradiated with the ultraviolet rays becomes a solid graft polymer 13.
[0041]
Next, as shown in FIG. 2 (h), the second mask material 12 is removed leaving the graft polymer 13, that is, the portion irradiated with ultraviolet rays. As a result, a second mask pattern 14 made of a graft polymer is formed on the surface of the protective film 11.
[0042]
Next, as shown in FIG. 3A, the protective film 11 and the gate insulating film 8 are wet etched using the second mask pattern 14, and the source region 7 a of the polysilicon island 7 is formed from the surface of the protective film 11. Contact holes 15 communicating with the drain regions 7b are formed. When this contact hole 15 is formed, the second mask pattern 14 is removed from the surface of the protective film 11 as shown in FIG.
[0043]
Next, as shown in FIG. 3C, a catalyst 33 for promoting plating is applied to the inner surface of the contact hole 15 and the signal line portion by an ink jet method.
Then, the protective film 11 and the glass substrate 1 are immersed in an electric field solution containing a wiring material, and the wiring material is attached and deposited only in the contact hole 15 and the signal line portion 21 where the catalyst 33 of the protective film 11 is applied.
[0044]
As a result, as shown in FIG. 3D, the wiring 17a and the wiring 17b connected to the source region 7a and the drain region 7b are formed. Nickel, copper, or the like is used as a material for the wiring material.
[0045]
Note that a conductive material such as nickel or copper is deposited by plating on the surface of the protective film 11 and in the contact hole 15, and then the conductive material is removed by wet etching leaving only the inside of the contact hole 15 and the signal line portion. The wiring 17a and the wiring 17b may be formed.
[0046]
This completes the manufacturing process of the thin film transistor.
[0047]
When manufacturing a TFT substrate used for a display device or the like using this thin film transistor, the following steps are further performed in addition to the above steps.
[0048]
4A to 4C are process diagrams showing a process for manufacturing the TFT substrate according to the embodiment.
[0049]
As shown in FIG. 4A, a liquid color resist material consisting of three colors of red, green, and blue is alternately applied to the entire surface of the protective film 11 by an inkjet method, and this color resist material is applied by a lamp. Heat cure. As a result, red, green, and blue color resists 18 are formed on the surface of the protective film 11. Here, only two color resists 18a and 18b of red, green and blue are shown.
[0050]
Next, as shown in FIG. 4B, the color resist 18 is wet-etched to form a contact hole 20 that communicates from the surface of the color resist 18 to the wiring 17b. Here, only the contact hole 20 formed in the color resist 18a is shown.
[0051]
Next, as shown in FIG. 4C, a liquid ITO film material is applied to the entire surface of the color resists 18a and 18b by an ink jet method, and the ITO film material is heated and cured by a lamp. As a result, an ITO film 19 connected to the wiring 17b is formed on the surface of the color resist 18 and inside the contact hole 20.
[0052]
Thus, the manufacturing process of the TFT substrate is completed.
[0053]
According to the thin film transistor and display device manufacturing method of the present invention, the base film 2, the polysilicon film 3, the first mask pattern 6, the gate insulating film 8, the gate electrode 10, the protective film 11, the second mask pattern 14, When forming the wiring 17a, the wiring 17b, the color resists 18a and 18b, and the ITO film 19, a method that does not use plasma, such as ink jet, lamp heating, atmospheric pressure chemical vapor deposition, or plating, is used. In addition, wet etching without using plasma is also used for etching.
[0054]
Therefore, since it is not necessary to create a high vacuum environment for generating plasma, productivity can be improved to the extent that the time required for this can be shortened.
[0055]
In addition, a graft polymerization material is used as the first and second mask materials 4 and 12, and this graft polymerization material is applied by an ink jet method, and a predetermined portion thereof is graft-polymerized by irradiation with ultraviolet rays, leaving a graft-polymerized portion. Thus, the first and second mask patterns 6 and 14 are formed by removing the first and second mask materials 4 and 12.
[0056]
Therefore, unlike the conventional case, it is not necessary to apply a photoresist by spin coating, so that the use efficiency of the material can be improved.
[0057]
Next, a second embodiment of the present invention will be described with reference to FIGS.
[0058]
In the present embodiment, the polymerization initiator 31 is applied to a predetermined portion of the surface of the polysilicon film 3 before applying the first mask material 4.
[0059]
This polymerization initiator 31 has the property of initiating graft polymerization of the first mask material 4. Therefore, as shown in FIG. 5A, if the polymerization initiator 31 is applied to the surface of the polysilicon film 3 where graft polymerization is desired, as shown in FIG. A predetermined portion of the first mask material 4 can be graft-polymerized only by applying the first mask material 4 from above.
[0060]
Then, as shown in FIG. 2C, the first mask pattern 6 can be formed on the surface of the polysilicon film 3 by removing the non-grafted portion of the first mask material 4. it can. Note that the technique of graft polymerization of the first mask material 4 using the above-described polymerization initiator 31 can naturally be used when forming the second mask pattern.
[0061]
The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the stage of implementation. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.
[0062]
【The invention's effect】
According to the present invention, productivity of a thin film transistor and a display device can be improved.
[Brief description of the drawings]
FIG. 1 is a process diagram showing a manufacturing process of a thin film transistor according to a first embodiment of the invention.
FIG. 2 is a process diagram showing a manufacturing process of the thin film transistor according to the embodiment.
FIG. 3 is a process diagram showing a manufacturing process of the thin film transistor according to the embodiment.
4 is a process diagram showing a manufacturing process of the display device according to the embodiment; FIG.
FIG. 5 is a process chart showing a manufacturing process of a thin film transistor according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Base film, 3 ... Polysilicon film, 4 ... 1st mask material, 5 ... Predetermined part, 6 ... 1st mask pattern, 7 ... Polysilicon island, 7a ... Source region, 7b DESCRIPTION OF SYMBOLS ... Drain region, 8 ... Gate insulating film, 9 ... Gate electrode material, 10 ... Gate electrode, 11 ... Protective film, 12 ... 2nd mask material, 13 ... Predetermined part, 14 ... 2nd mask pattern, 15 ... contact hole, 17a ... wiring, 17b ... wiring, 18a, 18b ... color resist, 19 ... ITO film, 20 ... contact hole, 21 ... signal line part, 31 ... polymerization initiator, 32, 33 ... catalyst.

Claims (9)

A base film forming step of applying a base film material to the surface of the substrate by an inkjet method to form a base film;
Forming an amorphous silicon film on the surface of the base film by plating or atmospheric pressure chemical vapor deposition, and polycrystallizing the amorphous silicon film, thereby forming a polysilicon film; and
A mask pattern forming step of forming a mask pattern made of a graft polymer on the surface of the polysilicon film;
And a polysilicon island forming step of forming a polysilicon island by etching the polysilicon film using the mask pattern. In a method for manufacturing a thin film transistor using a polysilicon film as a semiconductor layer,
Applying a gate insulating film material to the surface of the polysilicon film by an ink jet method to form a gate insulating film; and
And a gate electrode forming step of forming a gate electrode on a predetermined portion of the surface of the gate insulating film by plating. In a method of manufacturing a thin film transistor including a gate electrode on a surface of a polysilicon film via a gate insulating film,
An impurity implantation step of implanting impurities into the polysilicon film using the gate electrode as a mask;
A protective film forming step of forming a protective film for protecting the transistor by atmospheric pressure chemical vapor deposition on the surface of the gate insulating film;
A mask pattern forming step of forming a mask pattern made of a graft polymer on the surface of the protective film;
A contact hole forming step of forming a contact hole communicating with the polysilicon film from the surface of the protective film by etching the protective film and the gate insulating film using the mask pattern;
A method of manufacturing a thin film transistor, comprising: forming a wiring by plating at least inside the contact hole. In a method for manufacturing a display device having a thin film transistor,
A color resist forming step of applying a color resist material to the surface of the protective film by an ink jet method to form a color resist;
An ITO film forming step of forming an ITO film by applying an ITO film material to the surface of the color resist by an ink jet method, and producing a display device. A base film forming step of applying a base film material to the surface of the substrate by an inkjet method to form a base film;
Forming a polysilicon film by forming an amorphous silicon film on the surface of the base film by plating or atmospheric pressure chemical vapor deposition, and polycrystallizing the amorphous silicon film; and
A mask material is applied to the surface of the polysilicon film by an inkjet method, and a predetermined portion of the mask material is graft-polymerized, and then the mask material is removed while leaving the graft-polymerized portion. A first mask pattern forming step of forming a first mask pattern made of a graft polymer on the surface of the silicon film;
A polysilicon island forming step of forming a polysilicon island by etching the polysilicon film using the first mask pattern;
Applying a gate insulating film material to the surface of the polysilicon island by an inkjet method, and forming a gate insulating film; and
Forming a gate electrode by plating on a predetermined portion of the surface of the gate insulating film; and
An impurity implantation step of implanting impurities into the polysilicon film using the gate electrode as a mask;
A protective film forming step of forming a protective film for protecting the gate electrode by atmospheric pressure chemical vapor deposition on the surface of the gate insulating film;
A mask material is applied to the surface of the protective film by an ink jet method, and after a predetermined portion of the mask material is graft polymerized, the mask material is removed leaving the graft polymerized portion. A second mask pattern forming step of forming a second mask pattern made of a graft polymer on the surface of
A contact hole forming step of forming a contact hole communicating with the polysilicon film from the surface of the protective film by etching the protective film and the gate insulating film using the second mask pattern;
A wiring forming step of forming wiring by plating at least inside the contact hole;
A color resist forming step of applying a color resist material to the surface of the protective film by an ink jet method to form a color resist;
An ITO film forming step of forming an ITO film by applying an ITO film material to the surface of the color resist by an ink jet method, and producing a display device. In a method of manufacturing a thin film transistor, in which a thin film transistor is formed by repeating film formation and etching on the surface of a substrate,
A method of manufacturing a thin film transistor, wherein a high vacuum environment is not used when the film formation and etching are performed. In a method of manufacturing a thin film transistor, in which a thin film transistor is formed by repeating film formation and etching on the surface of a substrate,
A method of manufacturing a thin film transistor, wherein the film formation and etching are performed under normal pressure. In the method of manufacturing a thin film transistor, the method includes a step of etching the film using a mask formed on the surface of the film.
A method for producing a thin film transistor, characterized in that, when a mask is formed on the surface of the film, a liquid as a material for the mask is applied using a method other than spin coating. In a method of manufacturing a thin film transistor having a mask pattern forming step of forming an etching mask pattern on the surface of the film,
The mask pattern forming step includes
A mask material application step of applying a mask material to the surface of the film by an inkjet method;
A graft polymerization step of graft polymerizing a predetermined portion of the mask material;
And a removing step of forming the mask pattern by removing the mask material leaving a graft polymerized portion.

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