JP2001308335A - Method of manufacturing thin film transistor, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for improving performance of a transistor by reducing defects in a silicon film, in manufacturing a thin film transistor. SOLUTION: By a process for forming a silicon film on an insulating substrate, a process wherein heating at a temperature higher than or equal to 500 deg.C is performed, and a process wherein cooling is performed at a temperature lower than or equal to 250 deg.C while hydrogen radical treatment or oxygen radical treatment is performed, crystal defects due to dangling bonds or the like in the silicon film is effectively terminated by using hydrogen or oxygen, and increase of an ON current and improvement of the reliability of a thin film transistor are realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a thin film transistor using an amorphous silicon or polycrystalline silicon thin film.

[0002]

2. Description of the Related Art In recent years, flat displays centering on liquid crystals have been remarkably developed, and particularly in displays of OA equipment, personal computers and portable equipment, demands for higher definition and lower cost of pixels have been increasing. In terms of manufacturing technology, technical development for these is being advanced. Generally, in a liquid crystal display device or the like equipped with a thin film transistor, an active region of silicon is formed on a glass substrate, a gate electrode is formed in the vicinity of the center of the active region via a gate insulating film, and then both sides of the gate electrode are formed. A thin film transistor is formed by introducing an n-type or p-type impurity into the active region by ion implantation to form a source / drain region.

FIG. 9 is a top view of a so-called N-channel type transistor among conventional thin film transistors, and a top view and a cross-sectional view in the XY direction of the top view.

As shown in FIG. 9, an undercoat 202 made of a silicon oxide film for preventing diffusion of impurities from the glass substrate 201 is formed on a surface of a glass substrate 201 which is an insulating substrate. A silicon film 203 as a semiconductor thin film is formed, and a thin film transistor is provided. This thin film transistor is a silicon film 2
03, a gate insulating film 204 made of a silicon oxide film, and a gate electrode 205 made of chromium (Cr), which is a refractory metal, formed on the gate insulating film 204.
And a source / drain region 206 in which N-type impurities are introduced at a high concentration into the regions on both sides of the silicon film 203. A wiring 207 made of aluminum (Al) is formed in the source / drain region 206 and the gate electrode 205 via a contact window 208.

Here, the silicon film 203 is amorphous silicon or polycrystalline silicon deposited on the glass substrate 201 by the CVD method. When a silicon thin film is formed by a CVD method, it is very difficult to monocrystallize the silicon thin film, so that the silicon thin film is generally amorphous or polycrystalline. In addition, high-temperature polycrystalline silicon films and low-temperature polycrystalline silicon films, which are being developed in recent years, can also be formed by depositing amorphous silicon and then heating the silicon film only by high-temperature heat treatment or laser irradiation. However, single crystallization has not been achieved. In such an amorphous silicon film or a polycrystalline silicon film, distortion is present because silicon atoms are not regularly arranged, and also many crystal defects due to mismatch of bonding hands are present.

[0006] The crystal defects in these films hinder the movement of electrons (or holes) flowing in the amorphous silicon film or the polycrystalline silicon film when the thin film transistor is turned on.
There is a problem that the ON current is reduced.

Therefore, in a conventional method of manufacturing a thin film transistor, a method of depositing an amorphous silicon film or a polycrystalline silicon film and then performing a heat treatment at a high temperature of 600 ° C. or more to reduce defects and improve crystallinity. Or 300 ℃ ～ 4
The wafer is exposed to plasma using hydrogen gas under the condition of 00 ° C. to bond hydrogen to dangling bonds (hereinafter, referred to as dangling bonds) of silicon atoms (hereinafter, referred to as hydrogenation treatment), thereby electrically insulating defects. It is neutralized and its characteristics are improved.

[0008]

However, the above-described method of manufacturing a thin film transistor has the following problems.

First, in the method of reducing defects by performing a heat treatment at a high temperature of 600 ° C. or higher, defects are reduced by thermally inducing silicon atoms to move and crystallize the silicon atoms. However, in order to perform it efficiently, a high temperature of 1000 ° C. or more is actually required. Therefore, a quartz substrate that can withstand a high temperature of 1000 ° C. or higher is required as the insulating substrate. By using a quartz substrate, there remains a problem that the unit cost of the substrate is significantly higher than that of a general glass substrate, and that the size of the substrate is hindered. Even at a high temperature of 1000 ° C. or more, a single crystal cannot be obtained from the silicon film due to disorder of the crystal orientation, and the silicon film becomes a polycrystalline silicon film, and defects such as dangling bonds remain. Hydrogen treatment is required after the heat treatment because the hydrogen atoms that have been eliminated are released.

Next, in the hydrogenation treatment under the condition of 300 ° C. to 400 ° C., dangling bonds are activated by inducing silicon atoms at 300 ° C. to 400 ° C., and hydrogen atoms are added to the activated dangling bonds. Are bonded to neutralize, but the induction between 300 ° C. and 400 ° C. also activates the bond between the silicon atom and the hydrogen atom, so that the hydrogen atom is also separated. Therefore, in the conventional hydrogenation treatment, an equilibrium state of bonding and desorption of hydrogen atoms at a predetermined temperature is established, and there is a limit to reducing the defects by increasing the bonding ratio of hydrogen atoms. Further, the optimum temperature for hydrogenation needs to be determined experimentally, but there remains a problem that it is not possible to perform processing at a temperature corresponding to each of a plurality of crystal defects contained in the silicon film.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a thin film transistor that reduces crystal defects in a silicon film of the thin film transistor and increases the ON current of the transistor.

[0012]

In order to achieve the above object, a method for manufacturing a thin film transistor according to the present invention comprises a step of forming a silicon film on an insulating substrate, a step of heating to 500 ° C. or more, A step of cooling to 250 ° C. or less while performing a hydrogen radical treatment with a mixed gas containing a gas is provided. By forming a silicon film on an insulating substrate and then heating it to 500 ° C. or higher, moisture or hydroxyl groups adsorbed on the surface of the silicon film and in the film can be removed, and crystal defects of the silicon film can be improved. Next, by cooling to a temperature of 250 ° C. or less while performing a hydrogen radical treatment with a mixed gas containing a hydrogen gas from a temperature of 500 ° C. or more, the hydrogen gas passes through an optimal hydrogenation temperature for crystal defects in the silicon film in the cooling process. Thus, hydrogenation can be performed most efficiently, and the ON current of the thin film transistor can be increased.

The present invention further comprises a step of forming a silicon film on an insulating substrate, a step of heating to 500 ° C. or more, and a step of cooling to 250 ° C. or less while performing oxygen radical treatment with oxygen gas. It is. By heating to 500 ° C. or higher, moisture or hydroxyl groups adsorbed on the surface of the silicon film and in the film can be removed, and crystal defects of the silicon film can be improved. Further, by performing oxygen radical treatment with oxygen gas, it is possible to achieve neutralization by bonding oxygen atoms to dangling bonds. By cooling to a temperature lower than or equal to ° C., an oxygenation temperature optimal for crystal defects in the silicon film is passed during the cooling process, so that oxygenation can be performed most efficiently, and the ON current of the transistor can be increased. When a dangling bond is terminated by an oxygen atom, the bonding energy of silicon and oxygen is larger than the bonding energy of silicon and hydrogen. Electrons (or holes) flowing in the film are less likely to be desorbed due to collision, and the reliability of the transistor can be improved. In addition, excess silicon in a minute region is generated by oxidation of silicon, and the excess silicon moves to terminate defects in the silicon film due to silicon, thereby further reducing defects in the film. it can.

Here, the step of heating to 500 ° C. or higher comprises:
It is more preferable to heat at a pressure of 0.01 pa or less. When heating to 500 ° C. or higher, by setting the pressure to 0.01 pa or lower, the effect of removing moisture or hydroxyl groups adsorbed on the surface of the silicon film and in the film can be enhanced.

Further, the step of heating to 500 ° C. or more comprises 1 p
Heating can also be carried out in a nitrogen or inert gas stream at a pressure below a. By heating to 500 ° C. or higher in a flow of nitrogen or an inert gas at a pressure of 1 pa or less, water or hydroxyl groups released from the surface of the silicon film by the flow of gas can be removed from the surface of the silicon film. The partial pressure of water or a hydroxyl group can be reduced, and the effect of removing water or a hydroxyl group can be enhanced.

In the step of heating to 500 ° C. or more, the silicon film is formed by an RTA method using a halogen lamp or the like.
After heating to a temperature of 0 ° C. or more for a time of 10 seconds or less,
It can be quenched to below ℃. By heating to 800 ° C. or higher, crystal defects in the silicon film can be reduced. By heating the silicon film by the RTA method using a halogen lamp or the like, only the silicon film is heated and the substrate is removed from the silicon film. , The silicon film can be subjected to high-temperature heat treatment even when a glass substrate having a softening point of 600 ° C. or lower is used. Also, 800
By heating at 10 ° C. or more for 10 seconds or less and rapidly cooling to 600 ° C. or less, the entire insulating substrate can be prevented from being heated and deformed.

It is more preferable that the region heated to 800 ° C. or higher by the RTA method is only near the surface of the insulating substrate and near the silicon film. By setting the region heated to 800 ° C. or more only near the surface of the insulating substrate and near the silicon film, it is possible to prevent the entire insulating substrate from being heated and deformed.

In addition, the step of heating to 500 ° C. or more
It is preferable that the time maintained at 0 ° C. or higher is within 5 minutes. In the step of heating at 500 ° C. or higher, the amount of heat shrinkage of the insulating substrate can be minimized by keeping the temperature at 650 ° C. or higher within 5 minutes.

In the step of performing the hydrogen radical treatment, a mixed gas containing a hydrogen gas is introduced into a processing chamber, high-frequency power or the like is applied to generate plasma, and the insulating substrate on which the silicon film is formed is exposed to the plasma. It can be. By exposing the insulating substrate on which the silicon film is formed to the hydrogen gas plasma, the hydrogen gas is present in a state of active hydrogen radicals which are decomposed in the plasma, so that the bonding with the dangling bond of silicon becomes easy, and hydrogenation is performed. The effect of can be improved. Further, since hydrogen radical generation by application of high-frequency power is very easy, hydrogenation corresponding to a large substrate can be realized.

In the step of performing the oxygen radical treatment, a structure may be employed in which an oxygen gas is introduced into a treatment chamber, high-frequency power or the like is applied to generate plasma, and the insulating substrate on which the silicon film is formed is exposed to the plasma. it can. By exposing the insulating substrate with the silicon film to oxygen gas plasma,
Since oxygen gas exists in a state of active oxygen radicals in which plasma is decomposed in plasma, bonding with silicon dangling bonds is facilitated, and the effect of oxygenation can be improved. Further, since oxygen radical generation by application of high-frequency power is very easy, oxygenation corresponding to a large substrate can be realized.

In the step of cooling to 250 ° C. or less while performing the radical treatment, it is preferable to lower the temperature at a rate of 10 ° C./min or less. By lowering the temperature at a rate of 10 ° C./min or less while performing the radical treatment, a sufficient time for the silicon film to stay near the optimum temperature for hydrogenation or oxygenation can be sufficiently provided, and the rate of hydrogenation or oxygenation can be increased. be able to.

In the step of cooling to 250 ° C. or lower while performing the radical treatment, it is more preferable to lower the temperature at a rate of 5 ° C./min or lower. By lowering the temperature at a rate of 5 ° C./min or less, the rate of hydrogenation or oxygenation can be further increased.

The step of heating to 500 ° C. or more and the step of cooling to 250 ° C. or less while performing the radical treatment are performed by moving the heating region of the insulating substrate while the substrate is exposed to the radical treatment state. And then cooled to 250 ° C. or less. After heating the substrate at a temperature of 500 ° C. or more by moving the heating region of the insulating substrate while exposing the substrate to the radical processing state,
By cooling to 0 ° C. or less, the silicon film is always exposed to radicals. In the heated region, moisture or hydroxyl groups adsorbed on the surface and in the silicon film are desorbed / removed. Since the cooling starts from the next moment, hydrogenation or oxygenation is performed when the temperature passes the optimum temperature of the radical treatment during the cooling. Such partial heating can facilitate processing of a large substrate.

It is preferable that the step of heating to 500 ° C. or higher is after the gate insulating film is formed. By heating to 500 ° C. or higher after forming the gate insulating film, defects at the interface between the silicon film and the gate insulating film can be reduced, and the film quality of the gate insulating film can be improved at the same time. Increase can be achieved.

It is preferable that the step of heating to 500 ° C. or higher is performed after introducing impurities into the source / drain regions of the thin film transistor. By heating the source / drain region of the thin film transistor to 500 ° C. or higher after introducing the impurity into the source / drain region, the impurity can be simultaneously activated by heat treatment.

Preferably, the step of heating to 500 ° C. or higher is after forming the interlayer insulating film. By heating to 500 ° C. or higher after the formation of the interlayer insulating film, it is possible to simultaneously improve the film quality of the gate insulating film and the interlayer insulating film and activate the source / drain impurities.

The silicon film is preferably amorphous silicon or polycrystalline silicon deposited by the CVD method.

The silicon film is preferably low-temperature polycrystalline silicon obtained by heating amorphous silicon deposited by a CVD method with excimer laser to form polycrystalline silicon.

Further, the display device of the present invention is configured so that the thin film transistor manufactured by the above-described method for manufacturing a thin film transistor is used as a pixel driving element. By using a thin film transistor with a high ON current, high-speed pixel driving can be performed in a display device. Further, the ON current of the transistor can be increased.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for manufacturing a thin film transistor and a display device according to the present invention will be described below with reference to the drawings.

(First Embodiment) A method for manufacturing a thin film transistor according to a first embodiment of the present invention will be described with reference to FIG. FIGS. 1A to 1J are cross-sectional views showing a change in structure in a manufacturing process of an N-channel thin film transistor.

First, silicon is deposited on a glass substrate 1 as an insulator substrate shown in FIG. 1A to prevent diffusion of impurities from the glass substrate 1 and to prevent interface defects on the lower surface of the silicon film 3 which is a semiconductor thin film in an active region. An undercoat 2 made of an oxide film and a silicon film 3 are formed. Here, the silicon film 3 may be an amorphous silicon film or a polycrystalline silicon film. Further, the polycrystalline silicon film is formed by heat-treating the amorphous silicon film at a high temperature (such as an electric furnace or a laser). Anneal). In particular, if amorphous silicon deposited by a CVD (Chemical Vapor Deposition) method or a plasma-assisted CVD method, or polycrystalline silicon heated by excimer laser is used, there is an effect that it can be prepared by low-temperature treatment.

Next, a resist pattern 20 for forming an active region of silicon is formed (FIG. 1B).

Next, after etching the silicon film 3 using the resist pattern 20 as a mask, the resist pattern 2
0 is removed to form a gate insulating film 4 made of a silicon oxide film (FIG. 1C).

Next, molybdenum tungsten (Mo)
W) After depositing a gate electrode material 5 'made of a film, a resist pattern 21 is formed in a region where a gate electrode is to be formed (FIG. 1d).

Next, after the gate electrode material 5 'is etched using the resist pattern 21 as a mask to form the gate electrode 5, phosphorus (P) as an N-type impurity is ion-implanted at a low concentration to form a low-concentration impurity region. 6 (FIG. 1)
e). Part of this low concentration impurity region 6 will be
(Lightly Doped Drain) Used as region 6 '.

Next, after removing the resist pattern 21, a resist pattern 22 is formed on the channel portion (the silicon film below the gate electrode 5) and the region 6 'to be the LDD portion of the low concentration impurity region, Using the resist pattern 22 as a mask, phosphorus (P) as an N-type impurity is ion-implanted at a high concentration to form a high-concentration impurity region 7 (FIG. 1F).

Next, the resist pattern 22 is removed (FIG. 1g).

Next, an interlayer insulating film 8 made of a silicon oxide film is formed (FIG. 1h).

Next, after forming a high-concentration impurity region 7 serving as a source / drain of the TFT and a contact window 9 (not shown) which partially opens the gate electrode 5 (FIG. 1I), a wiring 10 is formed to form a thin film transistor. (Fig. 1
j).

FIG. 5 is a schematic view of a hydrogenation apparatus. In the hydrogenation processing, a substrate 58 is placed in a container 51 as shown in FIG. Warm up. The interior of the container 51 can be evacuated by opening a valve 57.
By means of and 56, a nitrogen gas or a hydrogen gas can be supplied into the chamber 52. Further, a hydrogen gas is introduced under reduced pressure, a high-frequency power is supplied to the electrode 54 to generate a plasma of the hydrogen gas to generate hydrogen radicals, and the hydrogen radicals are supplied to the substrate 58 so that the dangling bond of the silicon film is formed. A hydrogen atom is bonded to

The hydrogenation treatment of the first embodiment is shown in FIGS.
This will be described in more detail with reference to FIG.

FIG. 2 is a diagram for explaining the lapse of time of the temperature and pressure of the hydrogenation treatment and the discharge power of plasma generation according to the first embodiment. As shown in FIG. Is changed by changing the discharge power. FIG. 5 is a schematic diagram of a hydrotreating apparatus for performing the hydrotreating according to the first embodiment. Specifically, FIG.
The substrate on which the silicon film 3 of FIG.
5) After being placed in the room, the temperature is adjusted to room temperature (25
(° C.) to 525 ° C. at a rate of 10 ° C./min.
At the same time, the valve 57 is opened to evacuate the vessel 51 and the chamber 52 to a vacuum of about 0.02 pa.

After holding the vacuum state for about 20 minutes to remove moisture and hydroxyl groups on the silicon film surface and in the film, the valve 56 is opened (while controlling the flow rate) to introduce hydrogen gas into the chamber 52. After the hydrogen gas flow rate and pressure are stabilized, a discharge power such as a high-frequency power is supplied to the electrode 54 to generate hydrogen plasma in the chamber 52 and generate hydrogen radicals.

Next, while maintaining the hydrogen plasma, the heater 53 is controlled to lower the temperature to 200 ° C. or less at a rate of 10 ° C./min or less, preferably 5 ° C./min or less. At this time, the substrate is slowly cooled while being supplied with hydrogen radicals.
Hydrogenation is performed at a temperature corresponding to the defect. This allows
An efficient and high hydrogenation rate can be obtained, and the ON current of the thin film transistor can be increased.

Next, the discharge power is turned off and the bulb 56 is turned off.
The hydrogen gas supply is stopped by closing. Valve 57
Is closed to stop the evacuation, and then the valve 55 is opened to supply nitrogen gas into the container 51 and the chamber 52 to make it atmospheric pressure.

Finally, the substrate 58 is taken out and the hydrogenation process is completed.

In this embodiment, in the high temperature state (525)
(° C) for about 20 minutes has been described in the case where the gas is not supplied in a vacuum state. Alternatively, it is also possible to maintain the high temperature state at a pressure of 1 pa or less while supplying a nitrogen gas or an inert gas. It is. In that case, since the water or hydroxyl groups released from the silicon film surface by the flow of gas can be removed from the silicon film surface, the partial pressure of water or hydroxyl groups on the silicon film surface can be reduced, and the effect of removing water or hydroxyl groups can be obtained. Can be increased.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
It is a figure for explaining temperature and pressure of hydrogenation processing concerning the embodiment, and passage of time of discharge power of plasma generation.
In the second embodiment, the same hydrogenation treatment as in FIG. 2 described in the first embodiment is performed, but the high-temperature state (52
During the holding at 5 ° C.), by setting the pressure to a high vacuum state of 0.01 pa or less, the moisture or hydroxyl group desorbing effect on the silicon film surface and in the film can be enhanced,
The rate of hydrogen treatment in the subsequent step of exposing to hydrogen plasma can be increased.

(Third Embodiment) FIG. 4 is a diagram for explaining the lapse of time of the temperature and pressure of the hydrogenation treatment and the discharge power of plasma generation according to a third embodiment of the present invention. FIG. 5 is a schematic diagram of a hydrotreating apparatus for performing a hydrotreating process according to a third embodiment. Specifically, after the substrate 60 on which the silicon film 3 of FIG. 1a is formed is placed on the heater 65 in the load lock chamber 61 of the hydrogenation apparatus (FIG. 6), the heater 65 turns the room temperature (25 ° C.). To 525 ° C. at a rate of 10 ° C./min. at the same time,
The valve 81 is opened to evacuate the load lock chamber 61 to a vacuum. Next, after the gate valve 72 is opened and the substrate 60 is moved to the lamp heating chamber 62 by the transfer means (not shown), the substrate 60 is moved by the upper lamp 66 and the lower lamp 67.
Is heated rapidly to 825 ° C. This is called RTA (Rap
id Thermal Annealing) method. Thereafter, the upper lamp 66 and the lower lamp 67 are turned off to rapidly cool. At this time, by using a light source having a shorter wavelength such as a halogen lamp, the energy of the lamp is hardly absorbed by the transparent insulating substrate 1 or the undercoat 2 and the silicon film 3
, It is possible to heat almost only the silicon film 3 efficiently. In addition, even when heating at 800 ° C. or more by using a lamp, rapid heating and post-quenching are easy, and the time at which the substrate temperature becomes 650 ° C. or more can be set within 5 minutes, and heating is performed. Substrate shrinkage can be prevented. By setting the temperature of the silicon film 3 to a high temperature of 800 ° C. or more, hydrogen and oxygen in the silicon film 3 can be almost completely discharged simultaneously with the recovery of silicon defects. next,
The substrate 60 is moved to the plasma chamber 63. Plasma chamber 63
Inside, the substrate 60 moves sequentially from left to right in FIG. 6, and is maintained at a desired temperature by a plurality of heaters 69. In the plasma chamber 63, the exhaust valve 8 is supplied while supplying hydrogen gas.
By controlling the pressure by 3 and 84 and applying high-frequency power to the gas plate 68 to generate plasma, the substrate 60 is subjected to a hydrogenation treatment. Here, by setting the plurality of heaters 69 so that the substrate temperature sequentially decreases as the substrate moves, it is possible to expose the substrate to hydrogen plasma while gradually cooling the substrate. Here, in this embodiment, since the temperature before the exposure to the hydrogen plasma is higher than that in the above-described embodiment, the amounts of hydrogen and oxygen in the silicon film 3 are smaller than those in the above-described embodiment. Therefore, the bonding with hydrogen is more actively performed, and the efficiency of hydrogenation can be significantly increased.

The substrate 60 cooled to 200 ° C. or lower while being exposed to the hydrogen plasma in the plasma chamber 63 is transferred to the unload lock chamber 64 and then returned to the atmospheric pressure by nitrogen and taken out. Here, the operation of the gate valves 71 to 75 is not described, but it goes without saying that the gate valves 71 to 75 are opened and closed as necessary when the substrate is moved. In the plasma chamber 63, the substrate 60 is gradually cooled at a cooling rate of 10 ° C./min or less, preferably 5 ° C./min or less, so that a stable hydrogenation treatment can be performed. In addition, by heating the silicon film 3 at a temperature of 800 ° C. or more to 10 seconds or less in high-temperature heating by a lamp, heat conduction from the silicon film 3 prevents the entire substrate from becoming hot and causing deformation such as shrinkage. be able to.

(Fourth Embodiment) FIG. 7 shows a fourth embodiment of the present invention.
It is a schematic diagram of a hydrotreating device for performing a hydrotreating concerning an embodiment. Specifically, the silicon film 3 of FIG.
Is placed on a heater 65 in the load lock chamber 61 of the hydrogenation apparatus (FIG. 7), and then the heater 65 increases the temperature from room temperature (25 ° C.) to 525 ° C. at a rate of 10 ° C./min. Heat to At the same time, the valve 81 is opened to evacuate the load lock chamber 61 to a vacuum. next,
After opening the gate valve 72 and moving the substrate 60 to the plasma chamber 92 (by the transfer means not shown), the substrate 60 is moved to the plasma chamber 92 next. In the plasma chamber 92, the substrate 60 sequentially moves from left to right in FIG. 7, and is maintained at a desired temperature by a plurality of heaters 69. When the substrate 60 moves, the substrate 60 is partially heated rapidly by the lower surface lamp 90 and is heated to 825 ° C. (RTA method). Thereafter, the substrate is moved out of the heating area by the lamp 90 with the movement of the substrate 60, and is rapidly cooled to 600 ° C. or less, which is the set temperature of the heater 93 adjacent to the lamp part 90. At this time, the lamp 90 uses a light source having a shorter wavelength such as a halogen lamp, so that the energy of the lamp reaches the silicon film 3 without being absorbed by the transparent insulating substrate 1 or the undercoat 2 and almost reaches the silicon film. Only the film 3 can be efficiently heated. Further, by adjusting the moving speed of the substrate 60, the substrate temperature can be adjusted to 65 ° C.
The time at which the temperature reaches 0 ° C. or higher can be made within 5 minutes, and the substrate can be prevented from contracting due to heating. By setting the temperature of the silicon film 3 to a high temperature of 800 ° C. or more, hydrogen and oxygen in the silicon film 3 can be almost completely discharged simultaneously with the recovery of silicon defects. In addition, in the plasma chamber 92, the exhaust valves 82 to
By controlling the pressure by 84 and applying high-frequency power to the gas plate 91, plasma is generated, and the hydrogenation of the substrate 60 is performed. Here, by setting the plurality of heaters 69 so that the substrate temperature is sequentially decreased as the substrate moves, the substrate can be exposed to hydrogen plasma while being gradually cooled. While exposed to hydrogen plasma in the plasma chamber 92,
The substrate 60 cooled to 0 ° C. or lower is transferred to the unload lock chamber 64 and then returned to the atmospheric pressure by nitrogen and taken out. Here, the operation of the gate valves 71 to 75 is not described, but it goes without saying that the gate valves 71 to 75 are opened and closed as necessary when the substrate is moved. Further, the substrate 60 is controlled by a lamp 90 and a heater 93 in a plasma chamber 92.
After heating to 0 ° C or higher and quenching to 600 ° C or lower, 1
By slow cooling at a cooling rate of 0 ° C./min or less, preferably 5 ° C./min or less, stable hydrogenation treatment can be performed.

(Fifth Embodiment) In the fifth embodiment of the present invention, the same hydrogenation treatment as in the above-described first to fourth embodiments is performed, but in the fifth embodiment, the gate shown in FIG. After depositing the insulating film 4, a hydrogenation process is performed. Gate insulating film 4
In general, a silicon oxide film is often used and is deposited by a CVD method. However, if the film is deposited by the CVD method, the film density is low, or the film has a large amount of fixed charges due to defects in the film or at the interface with the silicon film 3. is there. Therefore, when heat treatment is performed after the formation of the gate insulating film, atomic movement occurs in a minute region due to thermal fluctuation of silicon and oxygen atoms, and the film quality is improved. Therefore, by performing the hydrogenation treatment including the heat treatment described in the first to fourth embodiments after depositing the gate insulating film 4, the dangling bonds in the silicon film are terminated with hydrogen, and the gate insulating film Can be obtained.

(Sixth Embodiment) In the sixth embodiment of the present invention, the same hydrogenation treatment as in the first to fourth embodiments is performed. In the sixth embodiment, the thin film transistor shown in FIG. After the impurities are implanted into the source / drain regions, hydrogenation is performed. Thus, in addition to the effect of reducing defects in the silicon film and the effect of improving the film quality of the gate insulating film described in the first to fourth embodiments, impurities in the source / drain regions can be activated.

(Seventh Embodiment) In the seventh embodiment of the present invention, the same hydrogenation treatment as in the first to fourth embodiments is performed. In the seventh embodiment, the thin film transistor shown in FIG. After the formation, a hydrogenation treatment is performed after the formation of the interlayer insulating film 8. Thus, in addition to the reduction of defects in the silicon film, the improvement of the film quality of the gate insulating film, and the activation of impurities, the interlayer insulating film 8 can be heat-treated, as described in the first to sixth embodiments. In addition, the quality of the interlayer insulating film 8 can be improved.

(Eighth Embodiment) Next, an eighth embodiment of the present invention will be described. The eighth embodiment performs substantially the same processing as the first to seventh embodiments, except that the substrate is exposed to oxygen plasma by using oxygen gas instead of hydrogen gas, and the silicon film is exposed to oxygen radicals. Oxygen is bonded to the dangling bond inside to terminate the oxidation.
At this time, the silicon is oxidized to generate surplus silicon in a minute region, and the surplus silicon moves to terminate a defect in the silicon film due to the silicon.
Defects in the film can be further reduced. In addition, since the bonding energy of silicon and oxygen is much larger than that of silicon and hydrogen, the once-bonded oxygen is in a stable state, so that electrons (or positive electrons) flowing in the silicon film when the transistor operates are performed. It becomes difficult to be desorbed by the collision of the holes, and the reliability of the transistor can be improved.

Note that the same silicon film may be subjected to both the hydrogen radical treatment using a mixed gas containing hydrogen gas and the oxygen radical treatment of the present embodiment.

(Ninth Embodiment) Next, a ninth embodiment of the present invention will be described. FIG. 8 is a diagram for explaining an active matrix display device using a thin film transistor manufactured by the method for manufacturing a thin film transistor of the present invention as a switching element, and the thin film transistor is arranged corresponding to each pixel of the flat display, One source region of the thin film transistors connected in the vertical direction is connected to a source wiring 101, and the other drain region is connected to a pixel electrode 103 for supplying a voltage to a display unit of each pixel. The gate wiring 102 is connected to a gate electrode of a thin film transistor that extends in the lateral direction. Therefore, the source wiring 101 and the gate wiring 102
And a voltage is applied to a desired pixel electrode 103. As the display portion, liquid crystal, electroluminescence, or the like can be used. By using a thin film transistor using the above-described manufacturing method for the switching element, the writing speed in the ON state of the switching is improved by reducing the defects in the silicon film, and the voltage due to the leak reduction effect in the OFF state is reduced. The holding capacity can be improved, and a high-definition, high-performance display device having a large display capacity can be obtained. Further, when a driving circuit (not shown) for driving a source and a gate using a thin film transistor according to the above-described manufacturing method is formed at the periphery of the substrate at the same time, the ON current of the thin film transistor is large. A driving circuit can be formed, and a display device with a narrow frame and a wide effective display area can be realized.

[0059]

As described in detail above, according to the method of manufacturing a thin film transistor of the present invention, the ON current of the thin film transistor can be increased and the reliability can be improved.

Further, it is possible to reduce crystal defects in the silicon film while preventing the entire insulating substrate from being heated and deformed in the manufacturing process of the thin film transistor, and to minimize the amount of thermal contraction of the insulating substrate. Can be.

Further, hydrogenation or hydrogenation of a silicon film corresponding to a large-sized substrate can be easily realized, and a sufficient time for staying near an optimum temperature can be taken, so that the ratio of hydrogenation or oxygenation can be increased.

Further, defects at the interface between the silicon film and the gate insulating film can be reduced, and the film quality of the gate insulating film can be simultaneously improved.

Further, activation of impurities and improvement of the film quality of the interlayer insulating film can be simultaneously performed.

When the thin film transistor according to the present invention is used in a display device, high-speed pixel driving is possible, which is effective for high-quality and high-definition display, and a compact and high-speed driving circuit can be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure change in a manufacturing process of an N-channel thin film transistor according to a first embodiment.

FIG. 2 is a diagram for explaining the time course of the temperature and pressure of the hydrogenation treatment and the discharge power of plasma generation according to the first embodiment.

FIG. 3 is a diagram for explaining a time course of a temperature and a pressure of a hydrogenation process and a discharge power of plasma generation according to a second embodiment.

FIG. 4 is a diagram for explaining a time course of a temperature and a pressure of a hydrogenation treatment and a discharge power of plasma generation according to a third embodiment.

FIG. 5 is a schematic diagram of a hydrotreating apparatus for performing the hydrotreating according to the first embodiment.

FIG. 6 is a schematic diagram of a hydrotreating apparatus for performing a hydrotreating process according to a third embodiment.

FIG. 7 is a schematic diagram of a hydrotreating apparatus for performing hydrotreating according to a fourth embodiment.

FIG. 8 is a view for explaining a display device using a thin film transistor manufactured by the manufacturing method according to the ninth embodiment of the present invention;

FIG. 9 is a diagram illustrating a conventional N-channel MIS transistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Undercoat 3 Silicon film 4 Gate insulating film 5 'Gate electrode 6 Low-concentration impurity region 7 High-concentration impurity region 8 Interlayer insulating film 9 Contact window 10 Wiring 20, 21, 22 Resist pattern

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/324 H01L 21/26 G 29/78 627G F term (Reference) 2H092 JA46 KA04 KA05 KA18 MA07 MA08 MA12 MA22 MA27 MA30 NA22 NA24 5F110 AA07 AA19 BB02 CC02 EE06 EE38 FF02 GG02 GG13 GG44 GG45 HJ01 HJ13 HM15 NN02 NN23 PP03 PP10 QQ25

Claims (18)

[Claims] A step of forming a silicon film on an insulating substrate; a step of heating the silicon film to 500 ° C. or higher;
Cooling the silicon film to 250 ° C. or lower while performing a hydrogen radical treatment with a mixed gas containing hydrogen gas. 2. A step of forming a silicon film on an insulating substrate; a step of heating the silicon film to 500 ° C. or higher;
Cooling the silicon film to 250 ° C. or lower while performing oxygen radical treatment with oxygen gas. 3. The method for manufacturing a thin film transistor according to claim 1, wherein the step of heating to 500 ° C. or higher includes heating at a pressure of 0.01 pa or lower. 4. The method for manufacturing a thin film transistor according to claim 1, wherein the step of heating to 500 ° C. or more is performed in a nitrogen or inert gas flow at a pressure of 1 pa or less. A method for manufacturing a thin film transistor. 5. The method for manufacturing a thin film transistor according to claim 1, wherein
The step of heating to a temperature of at least C.C.
A method for manufacturing a thin film transistor, comprising heating a silicon film to a temperature of 800 ° C. or higher for 10 seconds or less by a TA method, and then rapidly cooling the silicon film to 600 ° C. or lower. 6. The method of manufacturing a thin film transistor according to claim 5, wherein the region heated to 800 ° C. or more by the RTA method is only near the surface of the insulating substrate and near the silicon film. Production method. 7. The method for manufacturing a thin film transistor according to claim 1, wherein
The method of manufacturing a thin film transistor, wherein the step of heating at a temperature of 650 ° C. or more is performed for 5 minutes or less. 8. The method for manufacturing a thin film transistor according to claim 1, wherein the step of performing the hydrogen radical treatment includes introducing a mixed gas containing hydrogen gas into a treatment chamber, applying high frequency power or the like, and generating plasma. A method for exposing the insulating substrate on which the silicon film is formed to plasma. 9. The method for manufacturing a thin film transistor according to claim 2, wherein the step of performing the oxygen radical treatment includes introducing an oxygen gas into a treatment chamber and applying a high frequency power or the like to generate a plasma, A method for manufacturing a thin film transistor, comprising a step of exposing an insulating substrate having a film formed thereon. 10. The method for manufacturing a thin film transistor according to claim 1, wherein the step of cooling to 250 ° C. or less while performing the radical treatment is performed at a rate of 10 ° C./min or less. A method for manufacturing a thin film transistor. 11. The method for manufacturing a thin film transistor according to claim 10, wherein said radical treatment is performed while performing said radical treatment.
The method of manufacturing a thin film transistor, wherein the step of cooling to 0 ° C. or less is performed by lowering the temperature at a rate of 5 ° C./min or less. 12. The method of manufacturing a thin film transistor according to claim 1, wherein the step of heating to 500 ° C. or higher and the step of cooling to 250 ° C. or lower while performing radical processing include the step of: A method of manufacturing a thin film transistor, comprising: moving a heating region of an insulating substrate while exposing the substrate to a temperature of 500 ° C. or more, and then cooling the film to 250 ° C. or less. 13. The method of manufacturing a thin film transistor according to claim 1, wherein the step of heating to 500 ° C. or higher is after forming a gate insulating film. 14. The method for manufacturing a thin film transistor according to claim 1, wherein the step of heating to a temperature of 500 ° C. or higher is performed after introducing impurities into a source / drain region of the thin film transistor. A method for manufacturing a thin film transistor. 15. The method of manufacturing a thin film transistor according to claim 1, wherein the step of heating to 500 ° C. or higher is after forming an interlayer insulating film. 16. The method for manufacturing a thin film transistor according to claim 1, wherein the silicon film is
A method for manufacturing a thin film transistor, comprising amorphous silicon or polycrystalline silicon deposited by a VD method. 17. The method for manufacturing a thin film transistor according to claim 1, wherein the silicon film is
A method for manufacturing a thin film transistor, characterized by being a low-temperature polycrystalline silicon obtained by heating amorphous silicon deposited by a VD method with excimer laser to obtain polycrystalline silicon. 18. A display device using a thin-film transistor manufactured by the method for manufacturing a thin-film transistor according to claim 1 as a pixel driving element.