JP2009158883A - Thin-film transistor substrate, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a thin-film transistor substrate which can improve the characteristic of a TFT, and to provide a thin-film transistor substrate obtained by the manufacturing method. <P>SOLUTION: In the manufacturing method for the thin-film transistor substrate 1 having a gate insulating film 14g made of a silicon oxide, an oxygen plasma processing is performed just after forming the gate insulating film 14g (an insulating film 14). Thereafter, a water-vapor processing is performed after forming a gate electrode. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a thin film transistor substrate capable of improving the characteristics of the thin film transistor substrate, and a thin film transistor substrate obtained by the method.

  In an active matrix driving display device such as a liquid crystal display or an organic EL display, a thin film transistor (hereinafter also referred to as TFT) constitutes a switching element provided in each pixel and a peripheral circuit on a display substrate of the display device. It is used as a circuit element. Although TFTs are required to have as high performance as possible, their characteristics are affected by various factors. Among them, the most influential factor is the characteristics or properties of the gate insulating film that is in direct contact with the channel portion of the silicon semiconductor through which electricity flows. This tendency is particularly remarkable in the polysilicon TFT, and it is no exaggeration to say that the characteristics of the polysilicon TFT are determined by the characteristics or properties of the gate insulating film.

  In a polysilicon TFT, a silicon oxide film is often used as a gate insulating film because of its good compatibility with a polysilicon semiconductor film. As a technique for improving the performance of this silicon oxide film, a technique called high-pressure steam treatment has been proposed (see, for example, Patent Document 1). In this method, the TFT is heat-treated in a high-pressure steam atmosphere of 0.2 to 20 MPa and 150 to 600 ° C., thereby improving the properties of the silicon oxide film and its interface and improving the characteristics of the TFT. is there. Specifically, the high-pressure steam treatment is considered to have an action of changing the structure of silicon oxide or promoting dangling bonds to be oxidized, and as a result, the characteristics of the polysilicon TFT are improved. It is considered.

  By the way, there are two types of TFT structures: a bottom gate type (or reverse stagger type) mainly used for amorphous silicon TFTs and a top gate type (or planar type) mainly used for polysilicon TFTs. . In bottom-gate TFTs, the layer structure is in the order of gate electrode, gate insulating film, and silicon semiconductor film, and the gate insulating film and silicon semiconductor film are almost always formed as a process. High-pressure steam treatment for membranes is rarely used. On the other hand, in the top gate type TFT, after the gate insulating film is formed, the gate insulating film can be processed. Usually, the high-pressure steam processing proposed in Patent Document 1 is performed here.

The high-pressure steam treatment proposed in Patent Document 1 is more effective as the temperature is higher than other annealing treatments, and is at least 250 ° C. or higher (pressure is usually about 1.3 MPa). It is said that it is necessary to do.
Japanese Patent Laid-Open No. 11-97438 JP 2004-288864 A

  However, in the steam treatment under the above-described conditions, there is a problem that a pressure vessel that can withstand high temperatures and high pressures must be prepared as a TFT manufacturing apparatus. In addition, for example, even when the substrate on which the TFT is formed is an inexpensive glass substrate or plastic substrate with low heat resistance, there is a problem that high-pressure steam treatment including high temperature and high pressure is difficult to apply.

  To deal with such problems, for example, it is conceivable to perform steam treatment under conditions lower than the above temperature. However, as the treatment temperature is lowered, the effect of improving the TFT characteristics tends to be lowered. The reason for this is that the molecular motion of water vapor molecules decreases due to the low temperature, and the number of molecules of water vapor molecules contributing to the treatment decreases because the saturated vapor pressure of water vapor decreases.

  Note that Patent Document 2 proposes that high-pressure steam treatment may be performed after the silicon semiconductor film is formed, the gate insulating film is formed, the source-drain electrodes are formed, or the TFT is completed. However, the high-pressure steam treatment in this case is a treatment aimed at reducing the trap level density of the polysilicon film, and is different from the high-pressure steam treatment of Patent Document 1. In the document 2, oxygen plasma treatment is performed on the polysilicon film before forming the gate insulating film. However, the oxygen plasma treatment is performed directly for the purpose of improving the characteristics of the polysilicon film. ing.

  The present invention has been made in order to solve the above-described problems. The object of the present invention is to provide a TFT without applying a high-pressure steam treatment including a high temperature and a high pressure to the gate insulating film as in the prior art. It is in providing the manufacturing method of the thin-film transistor substrate which can improve the characteristic of this, and the thin-film transistor substrate obtained by the method.

  As a result of repeated research on the above problems, the present inventors have found that the oxygen plasma treatment and the water vapor treatment are performed on the gate insulating film as compared with the case where only the oxygen plasma treatment is performed or only the high pressure water vapor treatment is performed. It was found that the characteristics of the TFT can be improved by performing the steps in that order, and the present invention has been completed.

  That is, the method for manufacturing a thin film transistor substrate of the present invention is characterized in that in the method for manufacturing a thin film transistor substrate provided with a gate insulating film made of silicon oxide, the gate insulating film is subjected to an oxygen plasma treatment and then subjected to a water vapor treatment. And

  In this invention, it is considered that oxygen atoms are taken into at least the surface of the gate insulating film by the oxygen plasma treatment, and that oxygen atoms act to terminate dangling bonds existing in the gate insulating film by the subsequent water vapor treatment. It is done. According to the present invention, the TFT characteristics can be improved as in the prior art. In particular, TFT characteristics similar to those of the prior art can be obtained without performing the water vapor treatment at a high temperature and pressure as in the prior art.

  As a preferred embodiment of the method for producing a thin film transistor substrate of the present invention, the oxygen plasma treatment is performed under a temperature condition of 100 ° C. or higher and 200 ° C. or lower.

  As a preferred embodiment of the method for manufacturing a thin film transistor substrate of the present invention, oxygen plasma in the oxygen plasma treatment is generated in a chamber different from the treatment chamber of the thin film transistor substrate and introduced into the treatment chamber.

  As a preferred embodiment of the method for producing a thin film transistor substrate according to the present invention, the water vapor treatment is performed under conditions including a pressure exceeding 0.1 MPa and a saturated vapor pressure and a temperature not lower than 100 ° C. and not higher than 200 ° C. .

  As a preferred embodiment of the method for manufacturing a thin film transistor substrate of the present invention, the gate insulating film is formed by a sputtering method.

  As a preferred embodiment of the method for manufacturing a thin film transistor substrate of the present invention, a thin film transistor having at least a step of forming a silicon semiconductor film on the substrate, a step of forming the gate insulating film, and a step of forming a gate electrode in that order. In the substrate manufacturing method, the oxygen plasma treatment is performed before the gate electrode is formed.

  In the above aspect, the steam treatment is performed after the gate electrode is formed.

  In the gate electrode formation step, it is preferable that the electrode material be a metal of aluminum, tungsten, tantalum, or molybdenum, or an alloy or composite metal containing the metal.

  The thin film transistor substrate of the present invention for solving the above-mentioned problems is manufactured by the method for manufacturing a thin film transistor substrate according to the present invention.

  According to the method for manufacturing a thin film transistor substrate of the present invention, the TFT characteristics can be improved as in the conventional case, and in particular, the TFT characteristics as in the conventional case can be obtained without performing the water vapor treatment at a high temperature and pressure as in the conventional case. Obtainable.

  According to the thin film transistor substrate of the present invention, the TFT substrate manufacturing method of the present invention can provide a TFT substrate having excellent TFT characteristics and low cost. As a result, it is possible to provide a TFT substrate that can be applied to a liquid crystal display, an organic EL display, or the like that has a good manufacturing yield and excellent characteristics.

  Hereinafter, the manufacturing method of the thin film transistor substrate of the present invention and the thin film transistor substrate obtained by the method will be described in detail. In addition, this invention is not limited to the form of drawing or the following embodiment.

(Thin film transistor substrate)
FIG. 1 is a schematic cross-sectional view showing an example of a thin film transistor substrate obtained by the manufacturing method of the present invention. A thin film transistor substrate (hereinafter also referred to as “TFT substrate”) obtained by the manufacturing method of the present invention is a TFT substrate having a gate insulating film made of silicon oxide, and the gate insulating film was subjected to oxygen plasma treatment. This was obtained as a result of the subsequent steam treatment. For example, in FIG. 1, at least the polycrystalline silicon semiconductor film 13 (source side diffusion film 13s, channel film 13c and drain side diffusion film 13d), gate insulating film 14g, and gate electrode 15g are formed from the substrate 10 side. The top gate / top contact type TFT substrate 1 provided in this order was obtained by subjecting the gate insulating film 14g to oxygen plasma treatment and then water vapor treatment.

  More specifically, the TFT substrate 1 shown in FIG. 1 includes a substrate 10, an undercoat film 11 provided on the substrate 10 as necessary, and a polycrystalline silicon semiconductor film 13 (on the undercoat film 11). Between the source-side diffusion film 13s, the channel film 13c, and the drain-side diffusion film 13d), and the gate insulating film 14g provided on the polycrystalline silicon semiconductor film 13 mainly on the channel film 13c, and the gate insulating film 14g. An insulating film 14 provided on the polycrystalline silicon semiconductor film 13 so as to have a contact hole in the gate electrode, a gate electrode 15g provided on the gate insulating film 14g, a source electrode 15s and a drain provided through the contact hole It has an electrode 15d and a protective film 18 provided so as to cover the whole.

(Thin Film Transistor Substrate Manufacturing Method)
2 to 4 are process diagrams showing the manufacturing method of the TFT substrate of the present invention. The manufacturing method of the TFT substrate 1 of the present invention is characterized in that water vapor treatment is performed on the gate insulating film made of silicon oxide after oxygen plasma treatment, and more specifically, at least a silicon semiconductor film is formed on the substrate 10. 13, a step of forming a gate insulating film 14 g made of silicon oxide, and a step of forming a gate electrode 15 g in that order, and an oxygen plasma treatment before the gate electrode 15 g is formed. The film 14g is subjected to water vapor treatment before or after the gate electrode 15g is formed. Hereinafter, the TFT substrate 1 having the gate overlap structure shown in FIG. 1 will be described as an example in the order of the manufacturing steps shown in FIGS. 2 to 4. The manufacturing method of the TFT substrate of the present invention includes the following components: However, the present invention is not limited to these specific examples and illustrated process examples, and may be modified within the range having the above features of the present invention. For example, a TFT substrate having a self-aligned structure or a TFT substrate having an LDD structure may be used.

(Each component)
First, the substrate 10 is prepared. The substrate 10 forms a support substrate for the TFT substrate 1 and may be an organic substrate or an inorganic substrate. Examples of organic substrates include polyethersulfone (PES), polyethylene naphthalate (PEN), polyamide, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, polyether ether ketone, liquid crystal polymer, fluororesin, polycarbonate, and polynorbornene. An organic substrate made of resin, polysulfone, polyarylate, polyamideimide, polyetherimide, or thermoplastic polyimide, or a composite substrate thereof can be given. Such an organic substrate may have rigidity, or may be a thin flexible film having a thickness of about 5 μm to 300 μm. Use of a flexible organic substrate (also referred to as a plastic substrate) can be applied to a film display or the like because the TFT substrate 1 can be a flexible substrate.

  Moreover, as an inorganic substrate, a glass substrate, a silicon substrate, a ceramic substrate etc. can be mentioned, for example. The glass substrate may be a glass substrate for liquid crystal displays having a thickness of about 0.05 mm to 3.0 mm, or may be an inexpensive alkali-free glass substrate that is slightly inferior in heat resistance.

  Next, as shown in FIG. 2A, an undercoat film 11 is formed on the prepared substrate 10 as necessary. The undercoat film 11 is not an essential film. For example, (i) as an adhesion film for improving the adhesion between the silicon film 13 and the substrate 10, (ii) to relieve the stress of the film formed in the subsequent process. As a stress relaxation film, (iii) as a barrier film for preventing impurities in the substrate 10 from entering the TFT, or (iv) as a heat buffer film against heat applied in a subsequent process when a non-heat resistant substrate is used. Can be provided. Therefore, it is not necessary to provide a case where adhesion is good, there is no influence of stress, a barrier property need not be considered, or a non-heat resistant substrate is not used.

  The undercoat film 11 may be provided on the entire surface of the substrate 10 or may be provided only in a necessary region. In the example shown in FIG. 2A, the undercoat film 11 is formed on the entire surface.

  The undercoat film 11 is selected from the group of chromium, titanium, aluminum, silicon, chromium oxide, titanium oxide, aluminum oxide, silicon oxide, silicon nitride, and silicon oxynitride according to the purposes (i) to (iv) above. Formed of any material. For example, when used as an adhesion film, a metal-based inorganic film made of chromium, titanium, aluminum, silicon, or the like is preferably used. When used as a stress relaxation film or a thermal buffer film, chromium oxide, titanium oxide, oxide A compound film made of aluminum, silicon oxide, silicon nitride, silicon oxynitride, or the like is preferably used. When used as a barrier film, a compound film made of silicon oxide, silicon oxynitride, or the like is preferably used. These films may be provided as a single layer or two or more layers may be laminated depending on the purpose.

  The thickness when the undercoat film 11 is provided as an adhesion film varies slightly depending on the material constituting the film, but is usually preferably in the range of 1 nm to 200 nm, and preferably in the range of 3 nm to 50 nm. Is more preferable. In addition, when forming the metal type inorganic film which consists of chromium, titanium, aluminum, or silicon as the undercoat film | membrane 11, it is more preferable to exist in the range of 3-10 nm, and chromium oxide, titanium oxide, aluminum oxide In the case where a compound-based inorganic film made of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, or aluminum oxynitride is formed as the undercoat film 11, it may be in the range of 5 nm to 50 nm. More preferred. On the other hand, the thickness when the undercoat film 11 is provided as a stress relaxation film, a barrier film, or a thermal buffer film varies slightly depending on the material of the film actually formed, but the thickness is usually 100 nm or more and 1000 nm or less. In view of the film formation time, it is more preferably in the range of 100 nm to 500 nm.

  The undercoat film 11 can be formed by various methods such as a DC sputtering method, an RF magnetron sputtering method, and a plasma CVD method. In practice, a preferred method according to the material constituting the film is employed. Usually, a DC sputtering method, an RF magnetron sputtering method, or the like is preferably used.

Next, as shown in FIG. 2B, a non-doped amorphous silicon film 21 a is formed on the undercoat film 11. The amorphous silicon film 21a can be formed by various methods such as an RF magnetron sputtering method and a CVD method. For example, when the amorphous silicon film 21a is formed by the RF magnetron sputtering method, for example, the film thickness is 50 nm under the film forming conditions of film forming temperature: room temperature, film forming pressure: 0.2 Pa, and gas: argon. The film can be formed. Note that it is possible to form an amorphous silicon film by the CVD method, and in this case, it is possible to form a film at a film formation temperature of about 25 ° C. However, since SiH ₄ is used as a source gas, After film formation, dehydrogenation treatment at about 450 ° C. (about 1 hour in a vacuum) is required.

Next, as shown in FIG. 2C, laser irradiation 22 is performed to polycrystallize the amorphous silicon film 21a into a polycrystalline silicon film 21p. The laser irradiation 22 is a crystallization means for polycrystallizing the amorphous silicon film 21a into the polycrystalline silicon film 21p, and is performed using various lasers such as a XeCl excimer laser and a CW (Continuous Wave) laser. Can do. For example, when crystallization is performed using a XeCl excimer laser with a wavelength of 308 nm, as an example, pulse width: 30 nsec (FWHM (full width at half maximum)), energy density: 200 mJ / cm ^{2 to} 300 mJ / Cm ² and room temperature conditions.

  Next, as shown in FIG. 2D, a patterned silicon oxide film 23 is formed on the polycrystalline silicon film 21p. First, a silicon oxide film 23 is formed on the polycrystalline silicon film 21p, a resist film (not shown) is further formed, and then the resist film is patterned to pattern the silicon oxide film 23, and then the resist film is removed. Thus, the configuration shown in FIG. The patterned silicon oxide film 23 functions as a mask for shielding impurity ions added to a predetermined region of the polycrystalline silicon film 21p.

  The silicon oxide film 23 is formed to a thickness of about 50 nm to 150 nm by, for example, an RF magnetron sputtering method. The silicon oxide 23 and at least the polycrystalline silicon semiconductor film 13 to be described later are removed by wet etching using, for example, a 2% HF solution before the defect processing step. As the resist film to be patterned, for example, various commercially available positive photoresists are preferably used. The resist is applied to the entire surface by means of a spinner or the like, dried and cured, and formed to a thickness of about 700 nm, for example. The

After the silicon oxide film 23 is patterned, ion implantation 24 is performed as shown in FIG. In the ion implantation 24, for example, phosphorus (P) is implanted at an implantation voltage of 10 keV and a room temperature at a dose of 5 × 10 ¹⁴ ions / cm ² to 2 × 10 ¹⁵ ions / cm ² . As an implantation element, in addition to phosphorus, a known element that can be ion-implanted into the polycrystalline silicon film 21p, such as boron, antimony, and arsenic, may be arbitrarily selected and implanted. By such ion implantation, a source-side diffusion film 13s and a drain-side diffusion film 13d are formed in the polycrystalline silicon film 21p, and a channel film 13c is formed between both the films 13s and 13d.

Next, as shown in FIG. 3E, the silicon oxide film 23 is removed by a 2% HF solution or a dry etching method. The dry etching method is a method in which the silicon oxide film 23 is decomposed and removed with an etching gas, for example, a fluorine-based gas (for example, CF ₄ ) and an oxygen gas that has been turned into plasma in a vacuum vessel. Dry etching method, using a commercially available device called a dry etcher (not shown), for example, gas: CF ₄ gas, oxygen gas, gas flow _rate: CF 4/95 sccm, oxygen / 5 sccm, applying power: 500 W, pressure: 6 .6 Pa, treatment time: 10 minutes. Specifically, after the inside of the chamber is set to a predetermined gas atmosphere, a substrate in the TFT element manufacturing process is placed on the cathode electrode plate, and a high-frequency voltage is applied between the cathode electrode plate and the opposing anode electrode by an RF oscillator. A device for generating plasma by applying is used. This dry etching may be performed after an activation process described later.

  Here, although the silicon oxide film 23 is used as a mask for ion implantation, a resist film may be used as a mask for ion implantation instead of the silicon oxide film 23. In this case, the resist film is removed before the activation process described later.

Next, as shown in FIG. 3F, the formed source-side diffusion film 13s and drain-side diffusion film 13d are irradiated with an energy beam 25 to activate both films 13s and 13d. As the energy beam 25, the same XeCl excimer laser as described above can be used. As an example, the pulse width is 30 nsec (FWHM), the energy density is 100 mJ / cm ^{2 to} 250 mJ / cm ² , and the room temperature is used. Can do. Further, when the silicon oxide film 23 formed on the polycrystalline silicon film 21p is removed after the activation process, the silicon oxide film 23 is removed by wet etching or plasma etching before the defect processing step described below.

  After the activation process, a defect process using oxygen plasma is performed to reduce defects in the polycrystalline silicon film 21p. The oxygen plasma treatment here is a treatment in which the activated polycrystalline silicon film is exposed to a state in which plasma is generated by discharge in a gas atmosphere containing at least oxygen gas, and is trapped in the polycrystalline silicon film. Terminates dangling bonds that act as levels and defects that exist in crystal grain boundaries. Such oxygen plasma treatment has an effect of increasing the electrical conductivity of the polycrystalline silicon film.

  In the oxygen plasma treatment, for example, the inside of a chamber filled with oxygen gas is controlled to a pressure of, for example, 133 Pa, and between capacitively coupled parallel plate electrodes (two flat electrodes are placed facing each other). This is done by installing a substrate and generating plasma. In this capacitively coupled parallel plate electrode, the electrode on which the substrate is installed is grounded to a ground potential, the opposite electrode is connected to a power source, and examples of processing conditions include, for example, the substrate at a predetermined temperature of about 200 ° C. Plasma is generated at, for example, 13.56 MHz and 100 W under a heated temperature condition, and for example, oxygen plasma treatment is performed for 1 hour.

Next, as shown in FIG. 3G, dry etching is performed to form islands. As the etching gas, SF ₆ or the like can be used.

Next, as shown in FIG. 3H, an insulating film 14 made of silicon oxide is formed on the entire surface including the source side diffusion film 13s, the channel film 13c, and the drain side diffusion film 13d. A method for forming the insulating film 14 is, for example, using an RF magnetron sputtering apparatus, input power to an 8-inch SiO ₂ target: 1.0 kW (= 3 W / cm ² ), pressure: 1.0 Pa, gas: argon + O ₂ (50 %) Of silicon oxide having a thickness of about 100 nm is formed.

  In the step shown in FIG. 3H, after the insulating film 14 made of silicon oxide is formed, oxygen plasma treatment 26 is performed on the insulating film 14. The oxygen plasma treatment 26 is performed in a chamber adjusted to a predetermined plasma condition. For example, the inside of a chamber filled with oxygen gas is controlled to a pressure of 133 Pa, for example, and a substrate is placed between the electrodes of a capacitively coupled parallel plate electrode (a state where two flat electrodes are placed facing each other) to generate plasma. Generate and do. In this capacitively coupled parallel plate electrode, the electrode on which the substrate is installed is grounded to a ground potential, the opposite electrode is connected to a power source, and the substrate is heated at a predetermined temperature, for example at 13.56 Hz and 300 W. Plasma is generated and, for example, an oxygen plasma treatment 26 for 1 hour is performed. Note that the pressure of 133 Pa exemplified here and plasma conditions such as 13.56 Hz and 300 W are not particularly limited. Moreover, it is preferable to perform as the processing temperature of the oxygen plasma processing 26 at 100 degreeC or more and 200 degrees C or less. If the temperature of the oxygen plasma treatment 26 is less than 100 ° C., the effect may not be obtained due to insufficient treatment. On the other hand, if the temperature exceeds 200 ° C., the non-heat-resistant substrate is used when a non-heat-resistant substrate is used. May cause damage to the conductive substrate. From the viewpoint that a high treatment effect can be obtained, a more preferable temperature is 150 ° C. or higher and 200 ° C. or lower.

  By the way, as a method of the oxygen plasma treatment, a treatment in plasma using the above-described ordinary capacitively coupled parallel plate electrode may be used. In this case, a gate made of silicon oxide during the oxygen plasma treatment 26 is used. The insulating film 14g may be damaged by plasma. Since most of the damage caused by the oxygen plasma treatment is recovered by the steam treatment 28 described later, the damage caused by the oxygen plasma treatment 26 is essentially not a problem in this process. However, in order to keep the effect of the water vapor treatment 28 higher, the gate insulating film 14g is treated by transporting oxygen plasma generated in a plasma generated in a separate chamber, which is a method without plasma damage, that is, remote plasma. The method is preferred. That is, it is preferable to use a remote plasma apparatus that generates oxygen plasma in the oxygen plasma processing 26 in a chamber different from the processing chamber of the TFT substrate 1 and introduces it into the processing chamber. FIG. 5 is a schematic diagram showing an example of a remote plasma apparatus, and such a remote plasma apparatus can be used.

  Note that the oxygen plasma treatment 26 may be performed after the step illustrated in FIG. 4I, that is, after the insulating film 14 is selectively etched using a resist process to form the contact hole 27. However, after the gate electrode 15g is formed, oxygen during the oxygen plasma processing may hardly pass through the gate electrode 15g and reach the gate insulating film 14g. Therefore, the oxygen plasma processing is performed before the gate electrode 15g is formed. It is preferable to carry out. Note that the gate electrode 15g is not limited to the case where an electrode material having high oxygen permeability is used, or an electrode material that can be expected to improve oxygen mobility by water vapor treatment described later.

  Next, as shown in FIG. 4I, the contact hole 27 is formed by selectively etching the insulating film 14 on the source side diffusion film 13s and the drain side diffusion film 13d using a resist process. For example, after forming a resist film on the insulating film 14, the resist film is patterned by exposure and development by a resist process using a photomask. The insulating film 14 in the contact hole forming portion exposed by the patterning is wet etched using, for example, a 2% HF solution to form the contact hole 27, and then the resist film is removed by plasma ashing. The plasma ashing method is a method of removing only a resist by using an oxygen gas in a plasma etching method. Thus, the gate insulating film 14g provided on the polycrystalline silicon semiconductor film 13 mainly on the channel film 13c and the contact hole 27 between the gate insulating film 14g are provided on the polycrystalline silicon semiconductor film 13. The formed insulating film 14 is formed.

  Next, as shown in FIG. 4J, after depositing, for example, an aluminum (Al) film having a thickness of 200 nm on the entire surface, patterning is performed by wet etching to form a source electrode 15s, a drain electrode 15d, and a gate electrode 15g. To do. Note that the gate electrode 15g provided on the gate insulating film 14g is considered to probably act as a catalyst when the water vapor treatment described later is performed, and the water vapor provided by the water vapor treatment is converted into active atomic hydrogen or atomic state. It is considered that this acts to supply oxygen into the gate insulating film 14g. An electrode material for forming the gate electrode 15g is not particularly limited, and a material having a catalytic effect similar to that of aluminum can be used. For example, any one of tungsten, tantalum, and molybdenum, or the metal thereof is included. Alloys or composite metals are preferred. In addition, for the purpose of improving heat resistance, a metal material containing aluminum as a main raw material and added with other elements such as silicon exhibits the same effect and can be preferably used. The gate electrode 15g, the source electrode 15s, and the drain electrode 15d can be formed by other film formation processes such as sputtering.

  Next, as shown in FIG. 4K, steam treatment is performed. The water vapor treatment may be performed on the gate insulating film 14g before forming the gate electrode 15g, but is preferably performed after forming the gate electrode 15g on the gate insulating film 14g. By such a water vapor treatment, it is possible to perform two actions of the structure relaxation of the network structure of silicon oxide constituting the gate insulating film 14g and the dangling bond oxidizing action, and as a result, the characteristics of the gate insulating film 14g are improved. TFT characteristics can be improved. The conventional high-pressure steam treatment described in Patent Document 2 is generally performed immediately after the formation of the silicon semiconductor film in order to reduce the trap level density of the silicon semiconductor film. It is more effective to perform the treatment after forming the gate electrode 15g. The reason is not clear at present, but it is considered that active atomic hydrogen and atomic oxygen are generated by the catalytic effect of the metal layer constituting the gate electrode 15g, and a high effect is obtained by the action.

  The treatment conditions in the water vapor treatment step are preferably performed in an atmosphere composed of a temperature of 100 ° C. or more and 200 ° C. or less and a pressure exceeding 1 atm (0.1 MPa) and a saturated vapor pressure or less. Under these treatment conditions, the pressure is particularly preferably 20 atm (2.0 MPa) or less, and by performing the steam treatment at this pressure or less, there is an advantage that a pressure vessel corresponding to a high pressure is not required. For example, since the saturated vapor pressure at 250 ° C. is 39 atmospheres (3.9 MPa), in such a temperature condition, the pressure condition is lower than the saturated vapor pressure (for example, 1.0 MPa to 2.0 MPa). Is preferred.

  Moreover, it is preferable to perform the process conditions in a water vapor treatment process in the atmosphere which consists of the temperature of 150 to 200 degreeC, and a saturated vapor pressure. The steam treatment at the saturated vapor pressure is preferable because the condition management is easy if water is put in a slight excess in the pressure vessel. However, when the temperature is high, the pressure becomes considerably high, so the upper limit of the temperature is preferably 200 ° C. The saturated vapor pressure at each temperature is 5 atm (0.5 MPa) at 150 ° C., 10 atm (1 MPa) at 180 ° C., and 15 atm (1.5 MPa) at 200 ° C. The steam treatment performed under these conditions is particularly preferable industrially because the pressure can be easily applied.

  This water vapor treatment is particularly effective when the gate insulating film 14g is formed by sputtering. That is, the gate insulating film 14g made of silicon oxide can be formed at a temperature lower than 300 ° C. according to the film forming principle of the sputtering method, and impurities are hardly mixed in the sputtering method. For example, an inexpensive glass substrate having low heat resistance or A plastic substrate can be used. However, although the gate insulating film 14g formed by the sputtering method tends to deviate from the stoichiometric composition and the defect density at the interface with the silicon semiconductor film 13 tends to increase, the oxygen plasma treatment process and the water vapor treatment process in the present invention are performed. By applying in that order, dangling bonds in the gate insulating film made of silicon oxide can be terminated, and a particularly high modification effect (high mobility as a transistor and low interface state density of the gate insulating film) can be obtained. There is an advantage that On the other hand, when the gate insulating film 14g is formed by the CVD method, since the film formation uses a chemical reaction, an organic functional group derived from the raw material is already bonded to the dangling bond, and the portion to be modified is Since it is a structural distortion or a reaction that substitutes a functional group, the effect of oxygen plasma treatment and water vapor treatment is lower than that of a gate insulating film formed by sputtering. Therefore, when both are compared, it can be said that the gate insulating film 14g formed by sputtering is more preferable.

  The water vapor treatment is preferably performed after each electrode (gate electrode 15g, source electrode 15s, drain electrode 15d) is formed by etching, as shown in FIG. The reason for this is that if it is performed immediately after the electrode layer is formed (that is, before the electrode layer is etched), although depending on the material of the electrode layer, the electrode layer may be altered and etching may not be performed well. It is because there is sex.

  Finally, as shown in FIG. 4L, a protective film 18 is formed so as to cover the entire element. A preferable example of the protective film 18 is a silicon oxide film. The protective film 18 is preferably formed with a thickness of about 20 nm by, for example, RF magnetron sputtering. Thus, the TFT substrate 1 of one embodiment shown in FIG. 1 can be manufactured.

(Operation of oxygen plasma treatment and steam treatment)
Next, the reason why the oxygen plasma treatment 26 and the water vapor treatment 28 are performed in this order on the gate insulating film 14g will be described. In the present invention, the oxygen plasma treatment 26 is performed after the gate insulating film is formed, and then the water vapor treatment 28 is further performed on the gate insulating film 14g, thereby improving the characteristics of the gate insulating film 14g and the characteristics (charges) of the TFT substrate 1. Mobility, etc.) can be improved. As shown in FIGS. 3H and 4I, the gate insulating film 14g is formed by patterning after the insulating film 14 is formed on the entire surface, so that “oxygen plasma treatment for the gate insulating film 14g” is performed. "May be an oxygen plasma treatment for the insulating film 14 before patterning, or an oxygen plasma treatment for the gate insulating film 14g after patterning, but a gate electrode is formed on the gate insulating film 14g. Even if the oxygen plasma treatment is performed after the formation, the effect on the gate insulating film 14g usually does not occur unless the gate electrode is oxygen permeable.

  As described above, the oxygen plasma treatment 26 according to the present invention is performed on the gate insulating film 14g made of silicon oxide or the insulating film 14 made of silicon oxide before patterning the gate insulating film 14g. Is called. On the other hand, the conventional general oxygen plasma treatment is performed on a polycrystalline silicon film, and terminates dangling bonds that act as trap levels in the polycrystalline silicon film and defects present at grain boundaries. And, as a result, contributes to improvement of characteristics such as increasing electrical conductivity. On the other hand, the oxygen plasma treatment 26 in the present invention is performed after the gate insulating film is formed, and is not oxygen plasma treatment performed on the polycrystalline silicon film, but oxygen is introduced into the gate insulating film made of silicon oxide. This is a process for introduction.

  For example, when the oxygen plasma treatment 26 is performed under a high temperature condition (for example, 350 ° C. or higher) with high oxygen mobility, the association probability between oxygen and dangling bonds on the surface of the gate insulating film 14g where oxygen is sufficiently present. In addition, the probability of association between oxygen introduced into the gate insulating film 14g and the dangling bond is high, not limited to the surface, and it is considered that any part contributes to the disappearance of the dangling bond. However, when the oxygen plasma treatment 26 is performed under a low temperature condition (for example, 300 ° C. or lower) in which oxygen mobility is low, sufficient oxygen can be present on the surface of the gate insulating film 14g, and gate insulation can be performed. Although it is considered that a certain amount of oxygen can be introduced into the film 14g, it is considered that oxygen and dangling bonds are not associated with a high probability inside the gate insulating film 14g.

  At this time, it is considered that the ease of association of oxygen inside the gate insulating film 14g also depends on the film quality of silicon oxide constituting the gate insulating film 14g. For example, in the case where the gate insulating film 14g is made of silicon oxide having a columnar structure, it is considered that oxygen is likely to diffuse into the grain boundaries of the columnar structure. Of course, a higher temperature is more effective for this diffusion. Therefore, it is desirable that the processing temperature when the gate insulating film 14g is exposed to oxygen plasma is also higher.

  However, in the present invention, by performing the water vapor treatment after the oxygen plasma treatment, the gate insulating film 14g has a higher annealing effect than when the oxygen plasma treatment alone or the water vapor treatment alone is performed. I understood it. In other words, since the mobility of the network of the silicon oxide film (gate insulating film) can be remarkably improved by the water vapor treatment performed after the oxygen plasma treatment, the gate insulating film can be obtained without increasing the temperature of the oxygen plasma treatment. Oxygen can be sufficiently diffused within 14 g. Specifically, not only when the oxygen plasma treatment is performed under a high temperature condition of 350 ° C. or higher, but also when the oxygen plasma treatment is performed under a low temperature condition of 200 ° C. or lower, a gate insulating film is formed by a subsequent water vapor treatment. It is considered that the mobility of oxygen introduced into 14 g can be increased, and as a result, the association probability between oxygen and dangling bonds can be increased, and the disappearance of dangling bonds can be promoted. Note that the “annealing effect” refers to an effect of improving characteristics of a transistor, for example, by eliminating or inactivating an electrical defect present in an insulating film, that is, a defect level.

  In general, the water vapor treatment 28 promotes a structural change of silicon oxide by exposing the substrate after forming the gate insulating film 14g made of silicon oxide to a water vapor atmosphere of, for example, 0.1 MPa or more. It is a process to improve. This water vapor treatment is considered to have an effect of promoting structural change of the silicon oxide film and oxidation of dangling bonds by the action of water vapor, and as a result, the characteristics of the TFT can be remarkably improved. As in the annealing process for the gate insulating film, the steam process 28 is more effective as the process temperature is higher, and if a higher effect is desired, a temperature of 250 ° C. or higher is required at least. At a lower temperature, the effect of the treatment becomes lower as the temperature decreases. The reason is that the lower the temperature, the less the molecular motion and the lower the saturated vapor pressure of water vapor. For example, the number of molecules contributing to the treatment is reduced.

The steam treatment is considered to have two effects, that is, a structure relaxation effect of the silicon oxide network structure and a dangling bond oxidation effect. It is thought that the hydrogen bonding action of water molecules contributes to the structure relaxation effect of the network structure, and the activation energy of the network motion is reduced by the hydrogen bond, and the structure changes to a more stable energy state. It does not involve a reaction. On the other hand, since the dangling bond oxidation action is a reaction between water molecules and silicon, water molecules from which oxygen has been extracted, that is, atomic hydrogen, combines with other atomic hydrogen to form hydrogen gas from the inside of the film. It must be discharged or reacted with other water molecules and discharged in the state of H ₃ O ⁺ ions. It is considered that many such reactions occur in the high temperature region where the movement of molecules is active. However, at low temperatures where the mobility is low, it is considered that atomic hydrogen causes oxygen extraction and dangling bonds do not disappear.

  Further, as described above, when the water vapor treatment is performed at a high temperature, the effect of the treatment is high, so that it is also effective for defects other than the gate insulating film 14g (for example, defects in the polycrystalline silicon semiconductor film). Therefore, an increase in the effect due to the combination of the oxygen plasma treatment and the steam treatment becomes difficult to see. However, when the temperature of the water vapor treatment is low, for example, the degree of the effect on the polycrystalline silicon semiconductor film is not so high, so that the increase of the treatment effect by the combination of the oxygen plasma treatment and the water vapor treatment can be clearly seen. Incidentally, when only the oxygen plasma treatment is performed, the surface layer is only oxidized even if the treatment at 250 ° C. is performed.

(Other embodiments)
A method for manufacturing a TFT substrate of the present invention will be described by further illustrating a plurality of embodiments other than the first embodiment described above. In the following, (1) a second embodiment for manufacturing a TFT substrate having a self-aligned structure, (2) a third embodiment for manufacturing a TFT substrate having a self-aligned structure by a high-temperature process, and (3) a TFT having an LDD structure. Each example of the fourth embodiment for manufacturing a substrate and (4) the fifth embodiment for forming a circuit such as an RFID or an IC tag using a gate overlap structure will be described.

  (1) First, a second embodiment for manufacturing a self-aligned TFT substrate will be described. Since each process for manufacturing the TFT substrate having the self-aligned structure is substantially the same as the process of the first embodiment, the process order will be mainly described here.

  A manufacturing method of a TFT substrate having a self-aligned structure according to the second embodiment includes a silicon film forming process, a silicon film crystallization (laser irradiation) process, a silicon film defect termination process, an insulating film forming process, and an oxygen plasma process. Process, gate electrode layer deposition process, gate electrode etching process, ion implantation process, activation (laser annealing) process, silicon film islanding by etching (gate insulating film is also islanded at the same time), interlayer insulating film formation Each step includes a film process, an interlayer insulating film etching (a gate insulating film is also etched at the same time) process, a source / drain electrode layer film forming process, a source / drain electrode etching process, and a water vapor treatment process.

  This manufacturing method is also referred to as a so-called self-alignment process because ions are implanted using the etched gate electrode as a mask. In the above, the etching of the gate insulating film is performed at the same time as the silicon film islanding process, but this gate insulating film etching process is performed not after the silicon film islanding process but after the gate electrode etching process. Also good. In that case, the gate insulating film has the same shape as the gate electrode.

  In manufacturing a TFT substrate having such a self-aligned structure, conventionally, oxygen plasma treatment after the insulating film forming step has not been performed, but in the present invention, oxygen plasma treatment is performed after the insulating film forming step. Further, the water vapor treatment is performed after the interlayer insulating film forming step or after the source-drain electrode etching step. The self-alignment process has the merit that the formation of the gate insulating film and the gate electrode layer can be performed continuously. It is preferable to perform oxygen plasma treatment after the process. However, since the water vapor treatment in this case is a treatment for the gate insulating film through the interlayer insulating film, conditions (temperature, pressure, time) for allowing water vapor to permeate sufficiently are set.

  (2) Next, a third embodiment in which a TFT substrate having a self-aligned structure is manufactured by a high-temperature process that is generally performed will be described. The manufacturing method according to the third embodiment is a method for manufacturing a TFT substrate having a self-aligned structure similar to that of the second embodiment. In the second embodiment, activation is performed using a laser. On the other hand, the third embodiment is called a so-called high-temperature process in that activation is performed by heat treatment in a high-temperature atmosphere. Because of the lower temperature than the process, it is sometimes called the “low temperature polysilicon process”). Each process for manufacturing the self-aligned TFT substrate is substantially the same as the process of the first embodiment, and therefore, the process order will be mainly described here.

  The TFT substrate manufacturing method according to the third embodiment includes a silicon film forming process, a silicon film crystallization (laser irradiation) process, a silicon film defect termination process, a silicon film etching process, an insulating film forming process, and an oxygen plasma. Treatment process, gate electrode layer deposition process, gate electrode etching process, ion implantation process, thermal activation (eg, activation by heat treatment at around 500 ° C.) process, interlayer insulation film deposition process, interlayer insulation film etching (simultaneously gated) The insulating film is also etched), the source-drain electrode layer forming step, the source-drain electrode etching step, and the water vapor treatment step.

  This manufacturing method is also called a so-called self-alignment process because ions are implanted using the etched gate electrode as a mask, as in the second embodiment. In the above, the gate insulating film is etched at the same time as the interlayer insulating film etching process. However, the gate insulating film etching process is performed not after the interlayer insulating film etching process but after the gate electrode etching process. Also good. In that case, the gate insulating film has the same shape as the gate electrode. Further, the thermal activation step may be after the interlayer insulating film etching step, not after the ion implantation step.

  In manufacturing a TFT substrate having such a self-aligned structure, conventionally, oxygen plasma treatment after the insulating film forming step has not been performed, but in the present invention, oxygen plasma treatment is performed after the insulating film forming step. Further, the water vapor treatment is performed after the interlayer insulating film forming step or after the source-drain electrode etching step. As in the case of the second embodiment, the self-alignment process has an advantage that the formation of the gate insulating film and the formation of the gate electrode layer can be performed continuously. From the viewpoint of characteristics, oxygen plasma treatment is preferably performed after the insulating film formation step. However, since the water vapor treatment in this case is a treatment for the gate insulating film through the interlayer insulating film, conditions (temperature, pressure, time) for allowing water vapor to permeate sufficiently are set.

  (3) Next, a fourth embodiment for manufacturing a TFT substrate having an LDD structure will be described. The LDD (Lightly Doped Drain) structure is a structure in which a lightly doped region is provided at a so-called gate end as compared with a source diffusion region (source diffusion film 13s) and a drain diffusion region (drain diffusion film 13d) to relax an electric field and prevent deterioration. . By providing such an LDD structure, leakage current can be reduced and reliability can be improved. Note that the low concentration region formed in the silicon semiconductor film 13 is a region formed in the portion of the silicon semiconductor film located at the end portion (gate end) of the gate electrode when the TFT substrate is viewed in plan. .

  The manufacturing method of the LDD structure TFT substrate according to the fourth embodiment is for forming a low concentration region according to the LDD structure before and after the ion implantation step of the manufacturing method of the second or third embodiment. It can be configured by adding an additional ion implantation step and a mask formation step. That is, after the gate electrode etching step, an ion implantation step (for low concentration region formation), a mask formation step (for source-drain diffusion region formation), and an ion implantation step (for source-drain diffusion region formation) are configured in this order. Thereafter, the activation process is continued. Other steps are the same as those of the manufacturing method of the third embodiment, and in particular, the timing of oxygen plasma processing and water vapor processing and the effects thereof are also the same as those of the manufacturing method of the third embodiment. However, since the water vapor treatment in this case is a treatment for the gate insulating film through the interlayer insulating film, conditions (temperature, pressure, time) for allowing water vapor to permeate sufficiently are set.

  (4) Next, a more specific fifth embodiment will be described. In the fifth embodiment, a circuit such as an RFID (Radio Frequency Identification) or an IC tag using a gate overlap structure is formed. As a manufacturing method in this case, for example, in the manufacturing method of the first embodiment, after the last electrode (gate electrode, source electrode, drain electrode) etching step, an interlayer insulating film forming step, an interlayer insulating film etching step are further performed. The wiring electrode film forming step and the wiring electrode etching step can be added in that order. Other steps are the same as those of the manufacturing method of the first embodiment.

  Also in this manufacturing method, the oxygen plasma treatment is performed immediately after the insulating film forming step, and the water vapor treatment is performed after the interlayer insulating film forming step performed after the electrode etching step or after the last wiring electrode etching step. However, since the water vapor treatment in this case is a treatment for the gate insulating film through the interlayer insulating film, conditions (temperature, pressure, time) for allowing water vapor to permeate sufficiently are set. Note that since the interlayer insulating film functions as a passivation layer of the silicon semiconductor film, a protective film is not particularly required, but may be additionally formed. In that case, a protective film may be formed after the steam treatment.

  As a specific example to which the manufacturing method similar to the fifth embodiment can be applied, for example, when manufacturing an RFID having a self-aligned structure and an LDD structure, a reflective display (electronic paper, In the case of manufacturing a reflective liquid crystal, manufacturing a top emission type organic EL display, manufacturing a transmission type liquid crystal display, or manufacturing a bottom emission type organic EL display, the present invention is applied. Applicable.

  The following experimental examples and examples further illustrate the present invention.

(Experimental example 1)
A silicon wafer (P type, resistivity 10 Ωcm) was prepared, an insulating film made of silicon oxide having a thickness of 100 nm was formed thereon, and an aluminum electrode having a thickness of 200 nm was further formed to prepare a sample. Here, the gate insulating film made of silicon oxide is formed into an 8-inch SiO ₂ target with an input power of 1.0 kW (= 3 W / cm ² ), a pressure of 1.0 Pa, and a gas of argon + O ₂ (50%). The film was formed by RF magnetron sputtering under film conditions, and the aluminum electrode was also formed by sputtering.

  The oxygen plasma treatment was performed after forming the insulating film made of silicon oxide and before forming the aluminum electrode. This oxygen plasma treatment is performed by filling the chamber with oxygen gas and controlling the pressure to 133 Pa, using a capacitively coupled parallel plate electrode, setting the substrate side to the ground potential, and performing predetermined substrate heating. The electrode was connected to a power source and processed by applying 13.56 MHz and 300 W for 1 hour. On the other hand, the water vapor treatment was performed for 3 hours at a predetermined temperature and in a predetermined water vapor pressure atmosphere after forming the aluminum electrode.

  The evaluation was performed by measuring the density of defects present at the silicon / insulating film interface. Specifically, as shown in FIG. 6, the capacitance was measured by applying a voltage cyclically, and the defect density existing at the silicon / insulating film interface was evaluated from the change in the capacitance with respect to the voltage. The results are shown in FIG. The results shown in FIG. 7 are the results when the temperatures of the oxygen plasma treatment and the water vapor treatment are both 260 ° C. and 150 ° C.

As shown in FIG. 7, the defect density of the sample subjected to the oxygen plasma treatment (260 ° C.) and the water vapor treatment (260 ° C., 1.3 MPa) is 7 × 10 ¹⁰ / cm ² eV, and the water vapor treatment (260 ° C. , 1.3 MPa), the defect density of the sample was 8 × 10 ¹⁰ / cm ² eV, and the defect density of the sample that was not subjected to oxygen plasma treatment or water vapor treatment was 5 × 10 ¹² / cm ² eV. . The defect density of the sample subjected to oxygen plasma treatment (150 ° C.) and water vapor treatment (150 ° C., 0.5 MPa) is 1.2 × 10 ¹¹ / cm ² eV, and water vapor treatment (150 ° C., 0.5 MPa). ) Was 4.3 × 10 ¹¹ / cm ² eV, and the sample without oxygen plasma treatment and water vapor treatment was 5 × 10 ¹² / cm ² eV.

  From this result, when the oxygen plasma treatment and the water vapor treatment are used in combination with the case where only the water vapor treatment is performed on the gate insulating film, oxygen treatment is performed in both cases where the treatment temperature is 260 ° C. and 150 ° C. The defect density when the plasma treatment and the steam treatment were used together was the lowest.

On the other hand, from the viewpoint of the effect of reducing the defect density, it can be seen that the combination of oxygen plasma treatment and water vapor treatment at 150 ° C. is most effective. That is, in the case of treatment at 260 ° C., reducing effect when used in combination with oxygen plasma treatment and the steam treatment was ^{7 × 10 10/5 × 10} 12 = 0.014 times, reduction in the case of only steam treatment an ^{8 × 10 10/5 × 10} 12 = 0.016 times, the difference between contrast was 0.016 / 0.014 = 1.14 times, when treated with 0.99 ° C. is, reducing effect when used in combination with oxygen plasma treatment and the steam treatment was ^{1.2 × 10 11/5 × 10} 12 = 0.024 times, the effect of reducing the case where only steam treatment 4.3 × ¹⁰ 11/5 × 10 ¹² = 0.086 times, and the difference between them was 0.086 / 0.024 = 3.58 times. Therefore, it was found that it is preferable to use both the oxygen plasma treatment and the water vapor treatment in combination with the effect of reducing the defect density at a low temperature (150 ° C. in this experimental example). Reduction can be achieved.

Example 1
Next, the same processing conditions as those shown in Experimental Example 1 were applied to manufacture the TFT substrate 1 having the mode shown in FIG. The TFT substrate 1 uses a 0.7 mm thick glass substrate (Corning 1737) as the substrate 10, and a 300 nm thick buffer film made of silicon oxide as the undercoat film 11 (at the time of laser crystallization of the silicon film) A layer for protecting the glass substrate from the thermal damage is formed by sputtering, for example, and a non-doped amorphous silicon film 21a having a thickness of 50 nm is formed thereon by sputtering. Thereafter, the entire surface was irradiated with laser light (for example, XeCl excimer laser, 300 Hz oscillation, energy density 300 mJ / cm ^{2 on} the irradiated surface, laser pulse width 20 nsec) to form a polycrystalline silicon film 21p. A resist mask for ion implantation is formed on the polycrystalline silicon film 21p by photolithography, and then ion implantation is performed (P ions are implanted at 5 × 10 ¹⁴ ions / cm ² at an acceleration voltage of 10 keV). After removing the resist used for the mask, an excimer laser was irradiated as in the case of crystallization as an activation treatment of the implanted ions. However, the energy density on the irradiated surface was set to 200 mJ / cm ² . Thereafter, the silicon film is islanded by photolithography (dry etching using SF ₆ gas), and then input to an 8-inch SiO ₂ target: 1.0 kW (= 3 W / cm ² ), pressure: 1.0 Pa, A gate insulating film having a thickness of 100 nm made of a SiO ₂ film was formed by sputtering under the film forming conditions of gas: argon + O ₂ (50%). After forming the gate insulating film, oxygen plasma treatment was performed at 250 ° C. for 1 hour, and subsequently, a contact hole was formed in the gate insulating film by photolithography (etching using hydrofluoric acid), Thereafter, an electrode layer made of aluminum having a thickness of 200 nm was formed by sputtering, and an electrode pattern was formed by photolithography. Thereafter, the entire substrate was subjected to water vapor treatment under conditions of 260 ° C., 1.3 MPa, and 3 hours. The obtained TFT substrate was subjected to electrical measurement as a transistor (Agilent, electrical measuring instrument 4156C), and the mobility was calculated from the current-voltage characteristics.

(Example 2)
A TFT substrate of Example 2 was produced in the same manner as in Example 1 except that the temperature of oxygen plasma treatment was changed to 150 ° C. and the temperature and pressure of water vapor treatment were changed to 150 ° C. and 0.5 MPa in Example 1. .

(Comparative Example 1)
A TFT substrate of Comparative Example 1 was produced in the same manner as in Example 1 except that oxygen plasma treatment was not performed in Example 1 and only water vapor treatment was performed under the same conditions as in Example 1.

(Comparative Example 2)
A TFT substrate of Comparative Example 2 was produced in the same manner as in Example 1 except that oxygen plasma treatment was not performed in Example 1 and only water vapor treatment was performed under the same conditions as in Example 2.

(Comparative Example 3)
A TFT substrate of Comparative Example 3 was produced in the same manner as in Example 1 except that oxygen plasma treatment and water vapor treatment were not performed in Example 1.

(result)
The charge mobility of the TFT substrate of Example 1 in which oxygen plasma treatment (260 ° C.) and water vapor treatment (260 ° C., 1.3 MPa) was applied to the TFT substrate 1 was 170 cm ² / VsV, and water vapor treatment (260 ° C. , charge mobility of a TFT substrate of Comparative example 1 was subjected to only 1.3 MPa) is 150 cm ² / Vs, the charge mobility of the TFT substrate of Comparative example 3 also oxygen plasma treatment is not performed even steaming ^{1 cm} 2 / Vs. Further, the charge mobility of the TFT substrate of Example 2 subjected to oxygen plasma treatment (150 ° C.) and water vapor treatment (150 ° C., 0.5 MPa) was 110 cm ² / Vs, and water vapor treatment (150 ° C., 0.5 MPa). ), The defect density of the TFT substrate of Comparative Example 2 was 70 cm ² / Vs, and the charge mobility of the TFT substrate of Comparative Example 3 that was not subjected to oxygen plasma treatment or water vapor treatment was 1 cm ² / Vs.

  From this result, when the TFT substrate of Examples 1 and 2 in which oxygen plasma treatment and water vapor treatment are used in combination with the gate insulating film is compared with the TFT substrate of Comparative Examples 1 and 2 in which only water vapor treatment is performed, In both cases where the temperature was 260 ° C. and 150 ° C., the charge mobility was highest when the oxygen plasma treatment and the water vapor treatment were used in combination.

  Further, as described above, from the viewpoint of the effect of improving the charge mobility, it can be seen that the TFT substrates of Examples 1 and 2 using oxygen plasma treatment and water vapor treatment at 150 ° C. are most effective. That is, when treated at 260 ° C., the effect of improving the charge mobility of the TFT substrate of Example 1 using both the oxygen plasma treatment and the steam treatment is 170/1 = 170 times, and Comparative Example 1 in which only the steam treatment is performed. The effect of improving the charge mobility of the TFT substrate was 150/1 = 150 times, and the difference between the two was 170/150 = 1.13 times. The effect of improving the charge mobility of the TFT substrate of Example 2 using both the treatment and the steam treatment is 110/1 = 110 times, and the effect of improving the charge mobility of the TFT substrate of Comparative Example 2 using only the steam treatment is 70 / 1 = 70 times, and the difference between the two was 110/70 = 1.57 times. Therefore, it has been found that it is preferable to use both the oxygen plasma treatment and the water vapor treatment in the effect of improving the charge mobility at a low temperature (150 ° C. in this example and the comparative example). Thus, the charge mobility can be improved.

It is a schematic cross section which shows an example of the thin-film transistor substrate of this invention. It is explanatory drawing which shows the manufacturing process of the thin-film transistor substrate of this invention. FIG. 3 is an explanatory diagram showing a process that follows the manufacturing process of FIG. 2. It is explanatory drawing which shows the process of the continuation of the manufacturing process of FIG. It is a schematic diagram which shows an example of a remote plasma apparatus. It is a graph which shows the change of the capacity | capacitance component with respect to gate voltage in each process. It is a graph which shows the interface defect density in each process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 TFT substrate 10 Substrate 11 Undercoat film 13 Polycrystalline silicon semiconductor film 13s Source side diffusion film 13c Channel film 13d Drain side diffusion film 14 Insulating film 14g Gate insulating film 15s Source electrode 15g Gate electrode 15d Drain electrode 18 Protective film 21a Amorphous Silicon film 21p Polycrystalline silicon film 22 Laser annealing 23 Silicon oxide film 24 Ion implantation 25 Energy beam 26 Oxygen plasma treatment 27 Contact hole 28 Water vapor treatment

Claims (9)

  In the manufacturing method of the thin-film transistor substrate provided with the gate insulating film which consists of silicon oxides, after performing oxygen plasma processing with respect to the said gate insulating film, the manufacturing method of the thin-film transistor substrate characterized by the above-mentioned.   The method for manufacturing a thin film transistor substrate according to claim 1, wherein the oxygen plasma treatment is performed under a temperature condition of 100 ° C. or higher and 200 ° C. or lower.   3. The method of manufacturing a thin film transistor substrate according to claim 1, wherein oxygen plasma in the oxygen plasma treatment is generated in a chamber different from a processing chamber of the thin film transistor substrate and introduced into the processing chamber.   4. The thin film transistor substrate according to claim 1, wherein the water vapor treatment is performed under conditions including a pressure exceeding 0.1 MPa and a saturated vapor pressure and a temperature not lower than 100 ° C. and not higher than 200 ° C. 5. Production method.   The method for manufacturing a thin film transistor substrate according to claim 1, wherein the gate insulating film is formed by a sputtering method. In a method for manufacturing a thin film transistor substrate, comprising at least a step of forming a silicon semiconductor film on a substrate, a step of forming the gate insulating film, and a step of forming a gate electrode in that order.
The method for manufacturing a thin film transistor substrate according to claim 1, wherein the oxygen plasma treatment is performed before forming the gate electrode.   The method for manufacturing a thin film transistor substrate according to claim 6, wherein the water vapor treatment is performed after the gate electrode is formed.   The method of manufacturing a thin film transistor substrate according to claim 6 or 7, wherein, in the gate electrode formation step, an electrode material is any one of aluminum, tungsten, tantalum, and molybdenum, or an alloy or a composite metal containing the metal.   A thin film transistor substrate manufactured by the method for manufacturing a thin film transistor substrate according to claim 1.

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