JP2005093700A - Thin film transistor, method for manufacturing the same and method for manufacturing electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a thin film transistor by a small-sized low-priced apparatus in which the producibility is high, defects are small, a production yield is high, no disconnections occur at a step, a thin film can be formed at a low cost, and the cost is overwhelmingly lower than in the prior art; and further to provide an electronic device in which a cost is reduced by containing the thin film transistor. <P>SOLUTION: In a method for manufacturing the thin film transistor which has respective thin films consisting of a silicon film 14 in which an impurity concentration is controlled; insulating films 12, 16, 20, 26, and conductive films 22, 24, in a process of forming the insulating films 12, 16, 20, 26, a liquid material containing Peru hydro polysilazane is used, to form either one of an underlying insulating film 12, a gate insulating film 16, an interlayer insulating film 20 and a passivation insulating film 26. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a thin film transistor, a thin film transistor, and a method for manufacturing an electronic device.

In general, a thin film transistor is formed of a thin film such as a semiconductor film, an insulating film, or a conductive film. A thin film transistor used for a liquid crystal display device or the like uses a transparent conductive film.
Furthermore, insulating films used for thin film transistors include a base insulating film, a gate insulating film, an interlayer insulating film, and a passivation insulating film. Conventionally, the CVD (Chemical Vapor Deposition) method has been mainly used to form these insulating films (see, for example, Patent Document 1). In addition to the CVD method, an insulating film or an organic insulating film formed by SOG (Spin On Glass) may be formed. This is a method often used for the purpose of planarization and used alone. It is rarely used, and is used in combination with a film formed by the CVD method.

FIG. 13 is a diagram showing a standard process of film formation by a conventional general CVD method.
The substrate set in the CVD apparatus is evacuated after being moved to the load lock chamber, then moved to the heating chamber and then heated, and then moved to the process chamber to form a film. The process chamber has a heating mechanism for maintaining the substrate temperature, and a process gas necessary for film formation is introduced. After the pressure is stabilized, a high frequency is applied, and the introduced gas is converted into plasma to form a film. After film formation, the remaining process gas is purged, the substrate is moved to the load lock chamber, vented, and taken out to the atmosphere.
JP-A-10-173196

However, these CVD film formation methods have the following four problems in terms of process.
(1) Since the gas phase reaction is used, silicon particles are generated in the gas phase, and the production yield due to the contamination of the apparatus and the generation of foreign substances is reduced.
(2) Since the raw material is in a gaseous state, the film formation proceeds uniformly on a substrate having a concavo-convex surface, and thus a concavo-convex insulating film is formed, and it is difficult to obtain a flat insulating film. This causes disconnection of the wiring pattern.
(3) Since the substrate heating process is necessary and the film formation speed is slow, productivity is lowered.
(4) A plasma CVD method or the like requires a complicated and expensive high-frequency generator or vacuum device, and consumes a large amount of energy in the vacuum system or plasma system, leading to high product costs.

  The present invention has been devised in view of the above-described problems, and it is possible to form a thin film at a low cost by using a small and inexpensive apparatus with high productivity, few defects, high yield, no disconnection at a step portion. Therefore, it is an object to manufacture a thin film transistor at an overwhelmingly low cost as compared with the prior art. Furthermore, an electronic device in which cost reduction is achieved by including the thin film transistor is provided.

In order to achieve the above object, the present invention employs the following configuration.
The method of manufacturing a thin film transistor of the present invention is a method of manufacturing a thin film transistor having a silicon film, an insulating film, and a conductive film each having a controlled impurity concentration, and the step of forming the insulating film contains perhydropolysilazane. A feature is that at least one of a base insulating film, a gate insulating film, an interlayer insulating film, and a passivation insulating film is formed using a liquid material.
Here, perhydropolysilazane is a substance name of a compound having — (SiH 2 NH) — as a basic unit. Further, since the perhydropolysilazane is an inorganic polymer that is soluble in an organic solvent, it can be handled as a liquid material by being mixed with the organic solvent. In addition, perhydropolysilazane has a property of causing thermosetting shrinkage associated with a dehydrogenation reaction by baking at a high temperature in an inert atmosphere and converting it into SiN (silicon nitride) ceramics. In addition, when fired in the atmosphere or in an atmosphere containing water vapor, it has the property of reacting with water and oxygen to be converted into a dense SiO ₂ (silicon oxide) film.

Therefore, by using such perhydropolysilazane, an insulating film having a desired composition can be easily formed. Therefore, at least one of a base insulating film, a gate insulating film, an interlayer insulating film, and a passivation insulating film is used. One insulating film can be formed with a desired composition. For example, an insulating film having a high barrier effect can be formed by forming a film having a high nitrogen (N) content, and polarization can be generated by forming a film from which nitrogen is removed. It is possible to form an insulating film in which suppressed electrical insulation is suitably obtained.
In addition, when an insulating film formed using such perhydropolysilazane is compared with an organic / inorganic SOG, the organic SOG is easily etched by oxygen plasma treatment, and the inorganic SOG has a thickness of several hundred nm. There are problems such as easy cracking, and there is a disadvantage that it is difficult to use a single layer for an interlayer insulating film or the like. In contrast, an insulating film formed using perhydropolysilazane has an advantage that it has high crack resistance and oxygen plasma resistance, and can be used as a thick insulating film even to a single layer. In particular, it is effective to form the gate insulating film and the interlayer insulating film using perhydropolysilazane because the film quality and formation method greatly affect the electrical characteristics of the thin film transistor.
In addition, since the method using perhydropolysilazane does not use a gas phase reaction as compared with the case of using the conventional CVD method, silicon particles are generated in the gas phase as in the conventional method. The insulating film can be satisfactorily formed without causing a reduction in production yield due to contamination of the apparatus or generation of foreign matter.

In the method for manufacturing the thin film transistor, the step of forming the insulating film preferably applies the liquid material by using a liquid phase method.
The “liquid phase method” referred to here is a method of placing a liquid material in contact with a substrate, and includes a spin coating method, a slit coating method, a dip coating method, a spray method, a roll coating method, a curtain coating method, and a printing method. This means a droplet discharge method or the like. Since the basic configuration of the coating apparatus used in these methods is a stage or holder for holding the substrate and a mechanism for applying a liquid onto the substrate, the configuration of the coating apparatus is very simple.
Therefore, unlike the prior art, a complicated and expensive high-frequency generator or vacuum device is not required, and a large amount of energy is not consumed in the vacuum system or plasma system, so that a thin film transistor can be manufactured at low cost. It becomes. In addition, since a vacuum apparatus is not required, a mass production line can be constructed with an extremely small investment compared to the prior art, and the throughput of the manufacturing apparatus can be increased.

In addition, since the liquid material to be the insulating film is applied using a liquid phase method, for example, even if the base film to which the liquid material is applied has an uneven surface, the liquid material is filled so as to fill the unevenness. Therefore, the surface of the insulating film is planarized without forming a step. Therefore, disconnection of the wiring pattern formed in the upper layer of the insulating film does not occur, so that the yield of thin film transistors can be improved.
Further, in the liquid phase method, the application time of the liquid material is extremely short, and the liquid material is applied in a short time as compared with the CVD method in which the film forming speed is low, so that improvement in productivity can be achieved.

In the method for manufacturing the thin film transistor, it is preferable to perform the first heat treatment and the second heat treatment after applying the liquid material.
The “heat treatment” referred to here is a treatment for transforming the insulating film by heating the coating film made of the liquid material. As an apparatus used for such a heat treatment, a heat treatment apparatus such as an oven, a baking furnace, or an annealing furnace is used. Further, a method of performing heat treatment by irradiating the coating film with light may be used. In this method, a light irradiation device using a halogen lamp, a UV lamp or the like as a light source, a laser annealing device, or a lamp annealing device is used. It is done. Since the apparatus used for such heat treatment does not have a vacuum system, the structure is simple.
Accordingly, the heat treatment can be performed by an inexpensive apparatus.

In the method for manufacturing the thin film transistor, it is preferable that the first heat treatment removes a solvent contained in the liquid material.
In this way, since the solvent contained in the liquid material is removed, only perhydropolysilazane can remain on the substrate.

In the method for manufacturing the thin film transistor, it is preferable that the second heat treatment is performed by firing the perhydropolysilazane contained in the liquid material.
In this way, since perhydropolysilazane is fired, an insulating film can be formed on the substrate.

In the method for manufacturing the thin film transistor, the second heat treatment is preferably performed in an oxygen atmosphere from which moisture has been removed.
The oxygen atmosphere here means a state in which oxygen is supplied into a predetermined space.
As described above, perhydropolysilazane has a property of being converted into a SiN (silicon nitride) film by high-temperature baking in an inert atmosphere, and therefore, second in an oxygen atmosphere from which moisture has been removed as in the present invention. By performing this heat treatment, an insulating film made of a silicon oxide film containing nitrogen is formed.
Since the insulating film formed in this manner has a property of a barrier effect for preventing material diffusion, it is an optimal insulating film as a base insulating film or a passivation insulating film.

In the method for manufacturing the thin film transistor, the second heat treatment is preferably performed in an oxygen atmosphere to which moisture is supplied.
As described above, perhydropolysilazane has the property of being converted into a SiO ₂ film by firing in the atmosphere or in a steam-containing atmosphere, so that the second heat treatment is performed in an oxygen atmosphere supplied with moisture as in the present invention. As a result, the nitrogen component contained in the perhydropolysilazane is removed, and an insulating film made of a silicon oxide film is formed.
The insulating film formed in this way becomes a film that does not cause polarization, and becomes a dense film that can control the interface characteristics with the silicon film. Therefore, switching of a thin film transistor such as a gate insulating film or an interlayer insulating film is performed. It can be suitably employed as an insulating film that affects characteristics and electrical characteristics.

In the method for manufacturing the thin film transistor, the second heat treatment is preferably performed at a processing temperature in the range of 300 ° C. to 500 ° C.
Here, heat treatment at 300 ° C. or lower results in insufficient baking, resulting in an insulating film having poor film quality. Further, in manufacturing a thin film transistor having low-temperature polysilicon, a heat treatment at 500 ° C. or higher gives a thermal load to the low-temperature polysilicon, so that the heat treatment is not an actual processing temperature.
Therefore, in the present invention, since the second heat treatment is performed at a processing temperature in the range of 300 ° C. to 500 ° C., the film quality of the insulating film is good.

In the method of manufacturing the thin film transistor, the liquid material applying step, the first heat treatment step, and the second heat treatment step may be repeated a plurality of times, thereby It is preferable to form an insulating film.
In the step of forming the insulating film using the liquid phase method described above, a liquid material in which the perhydropolysilazane is contained at a predetermined concentration in a solvent such as xylene is used. The concentration of perhydropolysilazane contained in such a liquid material is generally determined according to the thickness of the insulating film after firing. Therefore, when an insulating film having a small thickness is formed, a liquid material having a low concentration is used. In the case of forming a thick insulating film, a liquid material having a high concentration is used.
However, when the concentration of the perhydropolysilazane is higher than a predetermined value, for example, when a liquid material is applied by using a spin coating method, there is a characteristic that the liquid material dropped on the substrate is difficult to spread to the peripheral portion.
In addition, since the thickness of the insulating film is increased, thermal stress is generated in the insulating film by performing the first heat treatment or the second heat treatment, which may cause defects such as cracks.

On the other hand, in the present invention, one insulating film is formed by repeatedly performing the step of applying the liquid material, the step of performing the first heat treatment, and the step of performing the second heat treatment. In other words, one insulating film can be formed by stacking a plurality of layers.
Therefore, the insulating film can be thickened using a liquid material having a low concentration without using a liquid material having a high concentration of perhydropolysilazane. Furthermore, the generation of cracks due to the first heat treatment or the second heat treatment does not occur, and an insulating film with good film quality can be formed.
In addition, when a liquid material having a low concentration of perhydropolysilazane is applied by using a spin coating method, the liquid material dropped on the substrate is preferably spread over the entire surface of the substrate, so that a flattened film is formed. It becomes easy.
The present invention is particularly effective for an insulating film that needs to be thickened. For example, the present invention is particularly effective for forming an interlayer insulating film or a passivation insulating film.

In the method for manufacturing the thin film transistor, the step of applying the liquid material and the step of performing the first heat treatment are repeatedly performed, and then the step of performing the second heat treatment is performed. It is preferable to form one insulating film.
Differences from the present invention described above, that is, the case where one insulating film is formed by stacking a plurality of insulating films, and the present invention will be described.
The above-described invention is a method of performing the second heat treatment every time the layers are formed, whereas the present invention is a method of performing the second heat treatment as the final step of the laminated film.
In this way, the same effects as those of the above-described invention can be obtained, and the second heat treatment need not be performed a plurality of times, so that the process can be simplified.

In the method of manufacturing the thin film transistor, the thin film transistor having a thin film of a silicon film, an insulating film, and a conductive film each having a controlled impurity concentration is characterized in that the thin film transistor is formed by the manufacturing method described above. Yes.
In this way, since the insulating film constituting the thin film transistor is formed using the above-mentioned perhydropolysilazane, an insulating film having a desired composition can be easily formed. That is, at least one of the base insulating film, the gate insulating film, the interlayer insulating film, and the passivation insulating film can be formed with a desired composition.
Further, since the thin film transistor is formed by using the liquid phase method, a complicated and expensive high-frequency generator or vacuum device is not required as in the prior art, and a large amount of energy is consumed in the vacuum system or the plasma system. In addition, since a vacuum device is not required, a mass production line can be constructed with very little investment compared to the conventional method, and the throughput of the manufacturing apparatus can be increased, so that a thin film transistor manufactured at a low cost. Can be provided.

According to another aspect of the present invention, there is provided a method of manufacturing an electronic device including a thin film transistor having a thin film of a silicon film, an insulating film, and a conductive film, each having a controlled impurity concentration. The thin film transistor is formed.
Here, as an electronic device, an active matrix substrate made of a thin film transistor, a flat panel display such as a liquid crystal device or an organic EL device having a driver circuit, and a device including the flat panel display as a display unit, such as a mobile phone, An information processing apparatus such as a mobile information terminal, a clock, a word processor, and a personal computer can be exemplified.
Other examples include a contact image sensor having the above-described thin film transistor, a driver built-in thermal head, a driver built-in optical writing element using an organic EL element as a light emitting element, and a three-dimensional IC.
In this way, an electronic device with reduced manufacturing cost can be provided.

Embodiments of the present invention will be described below with reference to the drawings.
In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

(Thin film transistor)
Two basic structural examples of the thin film transistor (hereinafter referred to as TFT) of the present invention are shown in FIGS. 1 and 2, respectively.
FIG. 1 is a cross-sectional view of a TFT using coplanar polycrystalline silicon. A base insulating film 12 is formed on the glass substrate 10, and a polycrystalline silicon TFT is formed thereon. In FIG. 1, the polycrystalline silicon layer 14 includes a source region 14S and a drain region 14D doped with impurities at a high concentration, and a channel region 14C between them.
A gate insulating film 16 is formed on the polycrystalline silicon layer 14, and a gate electrode 18 and a gate line (not shown) are further formed thereon. Through the opening formed in the interlayer insulating film 20 and the gate insulating film 16 thereunder, the pixel electrode 22 made of a transparent conductive film is connected to the drain region 14D, and the source line 24 is connected to the source region 14S. A protective film (passivation insulating film) 26 is formed on the uppermost layer. The base insulating film 12 is intended to prevent contamination from the glass substrate 10 and to prepare a surface state on which the polycrystalline silicon film 14 is formed, but may be omitted. Further, the protective film 26 may be omitted depending on the form of the TFT.

FIG. 2 is a cross-sectional view of a TFT using inverted staggered amorphous silicon. A base insulating film 32 is formed on the glass substrate 30, and an amorphous silicon TFT is formed thereon.
In FIG. 2, a single-layer or multi-layer gate insulating film 36 is formed under the gate electrode 34 and the gate line connected thereto. A channel region 38C of amorphous silicon is formed on the gate electrode 34, and further, source / drain regions 38S and 38D are formed by diffusing impurities in the amorphous silicon. The pixel electrode 40 is electrically connected to the drain region 38D via the metal wiring layer 42, and the source line 44 is electrically connected to the source region 38S. The metal wiring layer 42 and the source line 44 are formed at the same time.
Furthermore, a channel protective film (passivation insulating film) 46 is formed on the channel region 38C. The channel protective layer 46 is a film that protects the channel region 38C when the source / drain region films 38S and 38D are etched, and may be omitted.

1 and 2 show the structure of a basic TFT, and these variations are very diverse. For example, the coplanar TFT of FIG. 1 has a structure in which a second interlayer insulating film is provided between the pixel electrode 22 and the source line 24 in order to increase the aperture ratio and the interval between the pixel electrode 22 and the source line 24 is narrowed. It can be. Alternatively, for the purpose of reducing the wiring resistance of the gate line and the source line 24 (not shown) connected to the gate electrode 18 and making the wiring redundant, the gate line and the source line can be a multilayer film. Furthermore, a light shielding layer can be formed on or below the TFT element. In the inverted staggered TFT of FIG. 2 as well, multilayering of wirings and insulating films can be performed for the purpose of improving the aperture ratio, reducing wiring resistance, and reducing defects. In any of these improved structures, the number of thin film layers constituting the TFT is mostly increased with respect to the basic structure of FIG. 1 or FIG.
In the following embodiment, a case where various thin films constituting the thin film laminated structure shown in FIG. 1 and FIG. 2 are formed with an unnecessary coating film of a vacuum processing apparatus will be described and particularly mentioned as a feature of the present invention. As described above, a method of forming any one of various insulating films of a passivation insulating film such as a base insulating film, a gate insulating film, an interlayer insulating film, and a channel protective film by using a liquid material containing perhydropolysilazane. Detailed description.

(Material for forming insulating film)
The present invention is characterized in that perhydropolysilazane is used as a material that becomes an insulating film (coating type insulating film) by being heat-treated after being applied using a liquid phase method. Perhydropolysilazane is a substance name of a compound having — (SiH 2 NH) — as a basic unit. In the present embodiment, “polysilazane” (registered trademark) of Clariant Japan Co., Ltd. is used as perhydropolysilazane.
In addition, when H in [SiH2NH] n is substituted with an alkyl group (for example, a methyl group, an ethyl group, etc.), it becomes an organic polysilazane and may be distinguished from an inorganic polysilazane. In this embodiment, it is preferable to use inorganic polysilazane.

  Further, since this polysilazane is an inorganic polymer that is soluble in an organic solvent, it can be handled as a liquid material by being mixed with the organic solvent. In addition, polysilazane has the property of being heat-cured and contracted due to a dehydrogenation reaction when fired at a high temperature in an inert atmosphere and converted to SiN (silicon nitride) ceramics. In addition, it has the property of reacting with water and oxygen and being converted into a dense SiO2 (silicon oxide) film by being fired in the atmosphere or in an atmosphere containing water vapor.

In a method for forming an insulating film using polysilazane having such properties, polysilazane is mixed with a liquid such as xylene and then applied onto a substrate by, for example, a spin coating method. Further, as will be described in detail later, the substrate on which the polysilazane coating film is formed is heat-treated to be converted into a SiO ₂ film or a SiO ₂ film containing nitrogen.

In addition, when an insulating film formed using such polysilazane is compared with organic / inorganic SOG, organic SOG is easily etched by oxygen plasma treatment, and inorganic SOG has cracks even with a film thickness of several hundred nm. There is a problem that it is easy to occur, and there is a disadvantage that it is difficult to use a single layer for an interlayer insulating film or the like. In contrast, an insulating film formed using polysilazane has an advantage that it has high crack resistance and oxygen plasma resistance, and can be used as a thick insulating film even if it is a single layer. In particular, it is effective to form the gate insulating film and the interlayer insulating film using polysilazane because the film quality and formation method greatly affect the electrical characteristics of the TFT.
In addition, since the method using polysilazane does not use a gas phase reaction as compared with the case of using the conventional CVD method, the silicon particles are generated in the gas phase as in the conventional case. Insulating films can be satisfactorily formed without incurring a decrease in production yield due to contamination or generation of foreign matter.
In the present invention, at least one layer, preferably a plurality of layers of a thin film laminated structure is formed by a coating film other than an SOG film having a siloxane bond as a basic structure. As long as this condition is satisfied, the SOG film May be used additionally.

(Coating insulation film forming equipment)
FIG. 3 is a view showing a coating type insulating film forming apparatus for forming an insulating film by applying a liquid material containing the above polysilazane and then performing a heat treatment. FIG. 4 is a view showing a main part of a spin coater for applying the liquid material, and FIG. 5 is a view showing polysilazane stretched over the entire surface of the glass substrate by the spin coater.
As shown in FIG. 3, the coating type insulating film forming apparatus 100 includes a loader 101, a spin coater 102, a first heat treatment unit 103A, a second heat treatment unit 103B, an unloader 104, a coating solution storage unit 105, The control unit 106, the temperature control unit 107, and the exhaust equipment 108 are configured.
As shown in FIG. 4, the spin coater 102 includes a stage 130, a dispenser 134, and a nozzle 136 as main components.

(First Embodiment of Insulating Film Forming Method)
Next, a first embodiment of the insulating film forming method by the coating type insulating film forming apparatus 100 will be described.
First, the loader 101 takes out a plurality of glass substrates stored in the cassette one by one, and conveys the glass substrates to the spin coater 102. As shown in FIG. 4, the spin coater 102 vacuum-sucks the substrate 132 on the stage 130, and the polysilazane liquid material 138 is dropped onto the substrate 132 from the nozzle 136 of the dispenser 134. The dropped polysilazane liquid material 138 spreads in the center of the substrate as shown in FIG. The polysilazane liquid material 138 is a mixed liquid of polysilazane and xylene, and this liquid material is put in a container called a canister can and stored in the liquid storage unit 105 shown in FIGS. 3 and 4. The polysilazane liquid material 138 is supplied from the liquid storage unit 105 to the dispenser 134 via the supply pipe 140 and applied onto the substrate. Furthermore, as shown in FIG. 5, the polysilazane liquid material 138 is stretched and applied to the entire surface of the glass substrate 132 by the rotation of the stage 130. At this time, most of the xylene evaporates. The rotation speed and rotation time of the stage 130 are controlled by the control unit 106 shown in FIG. 3, and the rotation speed increases to 1000 rpm in a few seconds, is held at 1000 rpm for about 20 seconds, and then stops after a few seconds.

  In a method using such a spin coating method, even when unevenness occurs in the film below the coating film made of the polysilazane liquid material 138, the polysilazane liquid material 138 is applied by filling the uneven surface. Therefore, the surface of the insulating film formed using the polysilazane liquid material 138 is a flattened film without forming a step. That is, since the wiring pattern formed in the upper layer of the insulating film is not broken, the yield of TFT can be improved.

Next, heat treatment is sequentially performed by the first heat treatment unit 103A and the second heat treatment unit 103B.
In the first heat treatment unit 103A, xylene (solvent) contained in the polysilazane liquid material 138 applied on the substrate is removed. As a result, only polysilazane remains on the substrate. Further, the substrate is conveyed to the second heat treatment section 103B, polysilazane is baked, and an insulating film made of a desired composition having at least SiO ₂ is formed on the substrate.

Here, in the second heat treatment, an insulating film having a desired film quality can be formed by adjusting the treatment atmosphere.
One specific second heat treatment method is a method of performing heat treatment while supplying oxygen into a treatment chamber from which water vapor such as moisture has been removed. In this method, nitrogen constituting the original polysilazane remains in the insulating film, that is, a silicon oxide insulating film containing nitrogen can be formed. Further, since the insulating film formed by the second heat treatment has a barrier effect that prevents material diffusion, the insulating film is an optimal insulating film as a base insulating film or a passivation insulating film.

  Another second heat treatment method is a method in which heat treatment is performed while oxygen is further supplied into a treatment chamber to which water vapor such as moisture is supplied. In this method, nitrogen constituting the original polysilazane is removed, and an insulating film made of a silicon oxide film can be formed. Further, the insulating film formed by such second heat treatment becomes a film that does not cause polarization, and becomes a dense film that can control the interface characteristics with the silicon film. It can be suitably employed as an insulating film that affects the switching characteristics and electrical characteristics of a TFT such as a film.

In the second heat treatment unit 103B, after the above-described heat treatment in the first heat treatment unit 103A, the temperature is higher than the heat treatment temperature in the first heat treatment unit 103A and is about 30 at a temperature of 300 ° C. to 500 ° C. It is preferable to perform a heat treatment for min to 60 min. By performing the second heat treatment at such a temperature, it is possible to perform the treatment at a sufficient temperature necessary for firing, and to reduce thermal damage to the TFT having the low-temperature polysilicon.
Note that in the second heat treatment, heat treatment at a high temperature in a short time such as lamp annealing or laser annealing may be performed. By doing so, it is densified and the film quality and interface characteristics are improved.

The first and second heat treatments described above are controlled by the temperature control unit 107. The first and second heat treatment units 103A and 103B are arranged so that the tact time of the spin coater 102 matches the heat treatment time in order to increase the processing capability of the coating type insulating film forming apparatus. The lengths of 103A and 103B and the number of substrates accommodated in the furnace are set.
Further, in the spin coater 102, it is necessary to remove xylene vaporized with the application of the polysilazane liquid material 138, and it is necessary to exhaust xylene removed by the first heat treatment unit 103A to the outside. It is necessary to remove hydrogen, ammonia, and the like that are generated as polysilazane is fired in the second heat treatment section 103B. Therefore, at least the spin coater 102, the first heat treatment unit 103A, and the second heat treatment unit 103B require the exhaust equipment 108. The glass substrate on which the insulating film is formed by heat treatment is stored in the cassette by the unloader 104.

  The coating-type insulating film forming apparatus 100 shown in FIG. 3 does not require a complicated and expensive high-frequency generator or vacuum apparatus as compared with a conventional CVD apparatus, and consumes a lot of energy in a vacuum system or a plasma system. There is no. Furthermore, the device configuration is remarkably simple, so that the device price is significantly reduced. In addition, there are features such as higher throughput, easier maintenance, and higher operation rate of the apparatus as compared with the CVD apparatus. This feature can greatly reduce the manufacturing cost of the TFT.

In the coating type insulating film forming apparatus shown in FIG. 3, all the insulating films of the base insulating film 12, the gate insulating film 16, the interlayer insulating film 20, and the protective film 26 shown in FIG. 1 can be formed. Further, when an insulating film is additionally formed between the pixel electrode 22 and the source wiring 24, the surface of the insulating film is flattened by forming the additional insulating film as a coating film using the apparatus of FIG. This is particularly effective. The base insulating film 12 and the protective film 26 may be omitted.
In the TFT structure of FIG. 2, insulating films such as a base insulating film 32, a gate insulating film 36, and a channel protective film 46 can be formed.

  As described above, an insulating film having a desired composition can be easily formed by applying such a polysilazane by a liquid phase method such as a spin coating method and performing a first heat treatment and a second heat treatment. That is, at least one of the base insulating film, the gate insulating film, the interlayer insulating film, and the passivation insulating film can be formed with a desired composition. For example, by forming a film having a high nitrogen content, it is possible to form an insulating film having a high barrier effect, and by forming a film from which nitrogen is removed, generation of polarization is suppressed. It is possible to form an insulating film with favorable electrical insulation.

(Second Embodiment of Insulating Film Forming Method)
Next, a second embodiment of the insulating film forming method will be described.
In the present embodiment, portions different from those in the first embodiment will be described, and the same components will be denoted by the same reference numerals to simplify the description.
FIG. 6 is a view for explaining the present embodiment, and shows a state in which the interlayer insulating film 20 is formed in the manufacturing process of the TFT shown in FIG. In FIG. 6, the pixel electrode 22, the source line 24, and the protective film 26 are not formed.

  In the present embodiment, the step of applying the polysilazane liquid material 138 in the first embodiment, the first heat treatment step, and the second heat treatment step are repeated twice to form the interlayer insulating film 20. Is a feature point. Specifically, as shown in FIG. 6, after the first interlayer insulating film 20a is formed by the coating type insulating film forming apparatus 100, the second interlayer insulating film is further similarly formed by the coating type insulating film forming apparatus 100. 20b is laminated.

Next, the advantage of stacking a plurality of interlayer insulating films in this way will be described.
Generally, in the polysilazane liquid material 138, polysilazane is contained in a xylene solvent at a predetermined concentration. The concentration of the polysilazane is determined according to the thickness of the insulating film after firing. Therefore, when forming a thin insulating film, a liquid material having a low concentration is used. In the case of forming a thick insulating film, a liquid material having a high concentration is used. Thus, when the concentration of polysilazane is higher than a predetermined value, for example, when a liquid material is applied by using a spin coating method, the liquid material dropped on the substrate has a characteristic that it is difficult to spread to the peripheral portion and the insulating material is insulated. Since the thickness of the film is increased, the first heat treatment or the second heat treatment may cause thermal stress in the insulating film, leading to defects such as cracks.
On the other hand, in this embodiment, since the interlayer insulating film having a plurality of layers is formed by using the insulating film forming method in the first embodiment described above, a liquid material having a high polysilazane concentration is used. There is no need to increase the thickness of the insulating film using a liquid material having a low concentration. Furthermore, the generation of cracks due to the first heat treatment or the second heat treatment does not occur, and an insulating film with good film quality can be formed.
In addition, when a liquid material having a low polysilazane concentration is applied using a spin coating method, the liquid material dripped onto the substrate is suitably spread over the entire surface of the substrate, so that it is easy to form a flattened film. Become.
The method of forming a plurality of films in this way is effective particularly for an insulating film that needs to be thickened, and is particularly effective for forming an interlayer insulating film or a passivation insulating film, for example.

(Third Embodiment of Insulating Film Forming Method)
Next, a third embodiment of the insulating film forming method will be described.
In the present embodiment, portions different from those in the first embodiment will be described, and the same components will be denoted by the same reference numerals to simplify the description.
7-9 is a figure which shows the coating device used for 3rd Embodiment of the insulating film formation method. In the present embodiment, a liquid material (polysilazane liquid material) having the above polysilazane is used as the liquid to be applied.
In FIG. 7, a substrate 302 is vacuum-sucked on a stage 301. The liquid material is supplied from the liquid storage unit 307 to the dispenser head 304 through the supply pipe 306. The liquid material is further applied as a very large number of dots 303 on the substrate 302 from a plurality of nozzles 305 provided in the dispenser head 307.

  A detailed sectional view of the nozzle 305 is shown in FIG. FIG. 8 shows a structure similar to that of a head of an ink jet printer, and a liquid material is ejected by vibration of a piezo element. The liquid material accumulates in the cavity portion 313 from the inlet portion 311 through the supply port 312. The expansion and contraction of the piezo element 314 that is in close contact with the vibration plate 315 causes the vibration plate 315 to move, and the volume of the cavity 313 decreases or increases. The liquid material is discharged from the nozzle port 316 when the volume of the cavity 313 decreases, and the liquid material is supplied from the supply port 312 to the cavity 313 when the volume of the cavity 313 increases. For example, as shown in FIG. 9, a plurality of nozzle openings 316 are arranged two-dimensionally. As shown in FIG. 7, when the substrate 302 or the dispenser 304 is relatively moved, the liquid material is applied to the entire surface of the substrate. It is applied in the form of dots.

  In FIG. 9, the arrangement pitch of the nozzle openings 316 is several hundreds μm for the horizontal pitch P1 and several mm for the vertical pitch P2. The diameter of the nozzle port 316 is several tens of μm to several hundreds of μm. The discharge amount at one time is several tens of ng to several hundreds ng, and the droplet size of the discharged liquid material is several tens of micrometers to several hundreds of micrometers. The liquid material applied in the form of dots is a circle of several hundred μm immediately after being ejected from the nozzle 305. When the liquid material is applied to the entire surface of the substrate, the pitch of the dots 303 is set to several hundred μm, and the substrate is rotated for several seconds at a rotational speed of several hundred to several thousand rpm. The film thickness of the coating film can be controlled not only by the rotation speed and rotation time of the substrate but also by the diameter of the nozzle openings 316 and the pitch of the dots 303.

  This liquid material application method is an ink-jet type liquid application method, and is applied in the form of dots over the entire surface of the substrate. Therefore, the substrate is moved, for example, rotated so that the liquid material is applied to the portion without the liquid material between the dots 303. Therefore, the liquid material can be used efficiently.

  In addition, in the ink-jet liquid application, the diameter of the nozzle port 316 can be further reduced, so that it can be applied to a linear pattern having a width of 10 to 20 μm. If this technique is used for the formation of a silicon film or a conductive film, direct drawing without requiring a photolithography process is possible. If the TFT design rule is about several tens of micrometers, a liquid crystal display that does not use a CVD device, a sputtering device, an ion implantation or ion doping device, an exposure device, or an etching device by combining this direct drawing and a coating type thin film formation technique. The device can be manufactured. That is, the liquid crystal display device can be manufactured only by the ink jet type liquid coating apparatus according to the present invention and a heat treatment apparatus such as a laser annealing apparatus or a lamp annealing apparatus.

  In the present embodiment, the case where a liquid material having polysilazane is used has been described. However, the liquid material for forming a thin film, a resist used as a mask during photoetching, or the like is not limited to the liquid material. A material liquid for various coating films may be used.

  In addition, among the thin films constituting the TFT shown in FIGS. 1 and 2, a method for forming a film other than the insulating film uses a patterning method using a known photolithography technique or an impurity diffusion method such as an ion doping method. It is formed.

  In the above embodiment, the TFT active matrix substrate has been described as an example. However, other two terminals such as MIM (metal-insulation-metal) and MIS (metal-insulation-silicon) are used as the same active matrix substrate. A three-terminal element can be similarly applied to a method for manufacturing a pixel switching element. For example, a thin film stack structure of an active matrix substrate using MIM includes only a conductive layer and an insulating layer without including a semiconductor layer. In this case, the manufacturing method of the present invention can also be applied. Furthermore, the present invention may be applied not only to an active matrix substrate but also to a display element used for, for example, EL (electroluminescence) or the like regardless of liquid crystal. Furthermore, the manufacturing method of the present invention can be applied to thin film devices having various thin film laminated structures including a conductive layer and an insulating layer, such as a semiconductor device including a TFT and a DMD (digital mirror device), and further including a semiconductor layer. is there.

Next, an electronic device having a TFT manufactured by the above manufacturing method will be described.
FIG. 10 is a perspective view showing an example of a mobile phone.
In FIG. 10, reference numeral 1000 denotes a mobile phone body, and reference numeral 1001 denotes a liquid crystal display unit made of the above-described TFT active matrix substrate.
FIG. 11 is a perspective view showing an example of a wristwatch type electronic apparatus.
In FIG. 11, reference numeral 1100 denotes a watch body, and reference numeral 1101 denotes a liquid crystal display unit comprising the above-described TFT active matrix substrate.
FIG. 12 is a perspective view illustrating an example of a portable information processing device such as a word processor, a personal computer, or a mobile information terminal. In FIG. 12, reference numeral 1200 denotes an information processing apparatus, reference numeral 1201 denotes an input unit such as a keyboard, reference numeral 1202 denotes a liquid crystal display unit comprising the above-described TFT active matrix substrate, and reference numeral 1203 denotes an information processing apparatus main body.

Each of the electronic devices illustrated in FIGS. 10 to 12 includes the TFT active matrix substrate having the above-described thin film transistor, and thus the electronic device is manufactured with reduced manufacturing costs.
Further, the present invention is not limited to the liquid crystal display device, and examples include a flat panel display such as an organic EL device having an active matrix substrate and a driver circuit, and a device including the flat panel display as a display unit.
Other examples include a contact image sensor having the above-described thin film transistor, a driver built-in thermal head, a driver built-in optical writing element using an organic EL element as a light emitting element, and a three-dimensional IC.

1 is a side cross-sectional view for explaining a basic structure of a thin film transistor of the present invention. 1 is a side cross-sectional view for explaining a basic structure of a thin film transistor of the present invention. The apparatus block diagram which shows the coating type insulating film forming apparatus which forms the insulating film of this invention. FIG. 4 is a side sectional view showing a main part of the coating type insulating film forming apparatus of FIG. 3. The sectional side view which shows the film | membrane formed with the coating type insulating film forming apparatus of FIG. FIG. 6 is a side cross-sectional view illustrating an interlayer insulating film of a thin film transistor. The block diagram of the other liquid coating device in this invention. The elements on larger scale of the liquid application apparatus shown in FIG. The elements on larger scale of the liquid application apparatus shown in FIG. FIG. 11 illustrates an electronic device of the present invention. FIG. 11 illustrates an electronic device of the present invention. FIG. 11 illustrates an electronic device of the present invention. Explanatory drawing for demonstrating a prior art.

Explanation of symbols

12 ... Underlying insulating film 14 ... Polycrystalline silicon layer (silicon film)
16 ... Gate insulating film 20 ... Interlayer insulating film 22 ... Pixel electrode (conductive film)
24 ... Source line (conductive film)
26 ... Protective film (passivation insulating film)
38C: Amorphous silicon channel region (silicon film)
138: Polysilazane liquid material (perhydropolysilazane)

Claims (12)

In a method of manufacturing a thin film transistor having a thin film of a silicon film, an insulating film, and a conductive film in which the impurity concentration is controlled,
The step of forming the insulating film includes forming at least one of a base insulating film, a gate insulating film, an interlayer insulating film, and a passivation insulating film using a liquid material containing perhydropolysilazane. A method for manufacturing a thin film transistor.   2. The method of manufacturing a thin film transistor according to claim 1, wherein in the step of forming the insulating film, the liquid material is applied by using a liquid phase method.   3. The method of manufacturing a thin film transistor according to claim 1, wherein a first heat treatment and a second heat treatment are performed after applying the liquid material.   The method for manufacturing a thin film transistor according to claim 3, wherein the first heat treatment removes a solvent contained in the liquid material.   4. The method of manufacturing a thin film transistor according to claim 3, wherein the second heat treatment is performed by baking the perhydropolysilazane contained in the liquid material. 5.   6. The method of manufacturing a thin film transistor according to claim 3, wherein the second heat treatment is performed in an oxygen atmosphere from which moisture has been removed.   6. The method for manufacturing a thin film transistor according to claim 3, wherein the second heat treatment is performed in an oxygen atmosphere to which moisture is supplied.   8. The method for manufacturing a thin film transistor according to claim 5, wherein the second heat treatment is performed at a treatment temperature in a range of 300 ° C. to 500 ° C. 9.   One insulating film is formed by repeatedly performing the step of applying the liquid material, the step of performing the first heat treatment, and the step of performing the second heat treatment. A method for manufacturing a thin film transistor according to claim 1.   The step of applying the liquid material and the step of performing the first heat treatment are repeatedly performed, and then the step of performing the second heat treatment is performed to form one insulating film. The method for producing a thin film transistor according to claim 1, wherein the thin film transistor is a thin film transistor. In a thin film transistor having a thin film of a silicon film, an insulating film, and a conductive film in which the impurity concentration is controlled,
A thin film transistor formed by the manufacturing method according to claim 1. In a method for manufacturing an electronic device including a thin film transistor having a thin film of a silicon film, an insulating film, and a conductive film in which the impurity concentration is controlled,
11. A method of manufacturing an electronic device, wherein the thin film transistor is formed by the manufacturing method according to claim 1.

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