JP2006324368A - Thin-film transistor mounted panel and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film transistor (TFT) loaded panel of which the thin-film transistor formed on a plastic substrate will not peel due to interfacial delamination between the plastic substrate and a buffer layer, even if due to various thermal histories applied during a TFT manufacturing process. <P>SOLUTION: The thin-film transistor loaded panel has a polysilicon thin film 13 formed on a plastic substrate 10 through a buffer layer 12. An inorganic adhesion layer 11 is formed between the plastic substrate 10 and the buffer layer 12. The inorganic adhesion layer 11 is preferably any one selected from among chromium titanium, aluminum, silicon, chrome oxide, titanium oxide, aluminium oxide, silicon nitride, and silicon oxynitride, and the buffer layer 12 is preferably silicon oxide. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thin film transistor mounting panel and a manufacturing method thereof, and more particularly to a thin film transistor mounting panel having a structure in which a thin film transistor formed on a plastic substrate is difficult to peel from the plastic substrate, and a manufacturing method thereof.

  In an active matrix drive type display device, a polysilicon thin film transistor (hereinafter referred to as TFT) is used as a switching element provided in each pixel or a circuit element constituting a peripheral circuit on a display substrate of the display device. Yes. A liquid crystal display panel, which is one of active matrix drive type display devices, is often used for mobile display applications such as mobile phones and PDAs, and a panel with a TFT mounted with further weight reduction and impact resistance is desired. Yes. In recent years, a TFT mounting panel using a plastic substrate instead of a glass substrate has been proposed.

As manufacturing methods of a TFT mounting panel using a plastic substrate, two types of manufacturing methods are mainly known. One is a method in which a TFT is manufactured on a glass substrate by a conventional technique, and then the TFT is peeled off from the glass substrate, and the peeled TFT is bonded to a plastic substrate. The other is a method in which a plastic substrate is used and a TFT is directly formed on the plastic substrate via a buffer layer (see, for example, Patent Documents 1 and 2).
JP 2000-68518 A (paragraph number 0017) JP 2000-188402 A (paragraph number 0028)

  The former method can use a conventional technique of manufacturing a TFT on a glass substrate, so that a TFT having high performance can be manufactured. However, since a complicated process of peeling and bonding is added, an increase in manufacturing cost is inevitable. There is a difficulty.

  Since the latter method uses a plastic substrate, material costs and man-hours can be reduced as compared with the case of using a glass substrate, but peeling occurs at the interface between the plastic substrate and the buffer layer due to the thermal history applied during the TFT manufacturing process. Therefore, there is a problem that the TFT is easily peeled off from the plastic substrate. The thermal history applied during the TFT manufacturing process includes, for example, (i) laser annealing to convert amorphous silicon formed on a plastic substrate into polysilicon, and (ii) impurity ions added to a predetermined region of the polysilicon thin film. Laser annealing for thermal activation later, (iii) Oxygen plasma treatment for defect reduction treatment of polysilicon thin film, (iv) Leakage path at the interface between polysilicon and gate insulating film by eliminating dangling bonds on silicon surface Thermal history such as hydrogen plasma treatment for eliminating water, (v) drying treatment performed after each step, and the like.

  The present invention has been made in order to solve the above-described problems. The object of the present invention is to provide a thin film transistor formed on a plastic substrate and its buffer layer by various thermal histories applied during the TFT manufacturing process. It is an object to provide a thin film transistor mounting panel that does not peel based on the interface peeling between the thin film transistor and a method for manufacturing the same.

  In the course of studying to solve the above problems, the present inventor formed a plastic layer even when an inorganic adhesion layer was formed between the plastic substrate and the buffer layer, due to various thermal histories applied during the TFT manufacturing process. It was found that the thin film transistor formed on the substrate was not easily peeled off, and the present invention was completed based on the knowledge.

  That is, the thin film transistor mounting panel of the present invention is a thin film transistor mounting panel in which a polysilicon thin film is formed on a plastic substrate via a buffer layer, and an inorganic adhesion layer is provided between the plastic substrate and the buffer layer. It is formed.

  According to the present invention, an inorganic adhesion layer is formed between the plastic substrate and the buffer layer, so that even when various thermal histories are applied at the time of manufacturing the thin film transistor, the interface between the plastic substrate and the buffer layer is applied. Can be prevented from peeling. As a result, peeling of the thin film transistor formed over the plastic substrate can be prevented, and a thin film transistor mounting panel with a high manufacturing yield can be provided.

  In the thin film transistor mounting panel of the present invention, the inorganic adhesion layer may be made of any one selected from the group consisting of chromium, titanium, aluminum, silicon, chromium oxide, titanium oxide, aluminum oxide, silicon nitride, and silicon oxynitride. preferable.

  In the thin film transistor mounting panel of the present invention, the buffer layer is preferably silicon oxide.

  Since the buffer layer made of silicon oxide functions to prevent impurity ions contained in the plastic substrate or the inorganic adhesion layer from diffusing into the semiconductor thin film, it is possible to prevent deterioration of the characteristics of the semiconductor thin film.

  In order to solve the above problems, a method for manufacturing a thin film transistor-mounted panel according to the present invention includes a step of forming an inorganic adhesion layer on a plastic substrate, a step of forming a buffer layer on the inorganic adhesion layer, and a step of forming on the buffer layer. A process of forming an amorphous silicon thin film, a process of forming a polysilicon thin film by laser annealing the amorphous silicon thin film, and impurity diffusion by adding impurity ions to a predetermined region of the polysilicon thin film and then thermally activating by laser annealing Forming a region.

  According to this invention, since the inorganic adhesion layer is formed between the plastic substrate and the buffer layer, the inorganic adhesion layer acts to prevent peeling based on the thermal history applied in the subsequent process. As a result, it is possible to prevent interfacial peeling that occurs during the manufacturing process, and to improve the manufacturing yield.

  In the method for manufacturing a thin film transistor mounting panel according to the present invention, the inorganic adhesion layer is selected from any of the group consisting of chromium, titanium, aluminum, silicon, chromium oxide, titanium oxide, aluminum oxide, silicon nitride, and silicon oxynitride. It is preferable to become.

  As described above, according to the thin film transistor mounting panel of the present invention, even when various thermal histories are applied at the time of manufacturing the thin film transistor, peeling at the interface between the plastic substrate and the buffer layer hardly occurs. A thin film transistor mounting panel with high manufacturing yield can be provided because peeling of the thin film transistor formed over the substrate can be prevented.

  According to the method for manufacturing a thin film transistor-equipped panel of the present invention, the formed inorganic adhesion layer acts to prevent peeling based on the thermal history applied in the subsequent process, so that it is possible to prevent interface peeling that occurs during the manufacturing process. And the manufacturing yield can be improved.

  Since the thin film transistor mounting panel of the present invention has TFTs formed on a flexible plastic substrate, a flexible display can be designed by combining with an organic EL element, for example.

  Hereinafter, the thin film transistor mounting panel and the manufacturing method thereof according to the present invention will be described in detail. FIG. 1 is a schematic cross-sectional view showing an example of a TFT element portion of a thin film transistor mounting panel according to the present invention, and FIGS. 2 and 3 are explanatory diagrams showing manufacturing steps of the thin film transistor mounting panel according to the present invention. In addition, this invention is not limited to the form of drawing or the following embodiment.

  The thin film transistor mounting panel of the present invention is formed by forming a polysilicon thin film on a plastic substrate through a buffer layer, and can be used, for example, as a display panel constituting an active matrix drive type display device. is there. The present invention is characterized in that an inorganic adhesion layer is formed between the plastic substrate and the buffer layer.

  More specifically, as shown in FIG. 1, the TFT element portion 1 of the thin film transistor mounting panel of the present invention is formed on a plastic substrate 10, an inorganic adhesion layer 11 formed on the plastic substrate 10, and an inorganic adhesion layer 11. Buffer layer 12, polysilicon semiconductor thin film 13 (source side diffusion film 13 s, semiconductor channel film 13 c and drain side diffusion film 13 d) formed on buffer layer 12, and polysilicon semiconductor thin film 13. And an electrode 15 (a source electrode 15s, a gate electrode 15g, and a drain electrode 15d) formed on the gate insulating film 14 or through a contact hole of the gate insulating film. In the following, the structure form of the TFT element portion shown in FIG. 1 will be described as an example in the order of the manufacturing steps based on FIGS. 2 and 3, but the thin film transistor mounting panel of the present invention and the manufacturing method thereof will be described in the illustrated example. The present invention is not limited, and other forms may be used as long as the inorganic adhesion layer is formed between at least the plastic substrate and the polysilicon semiconductor thin film formed through the buffer layer.

  The plastic substrate 10 forms a circuit board of a thin film transistor. For example, polyether sulfone (PES), polyethylene naphthalate (PEN), polyamide, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, polyether ether ketone, liquid crystal The organic base material which consists of a polymer, a fluororesin, a polycarbonate, a polynorbornene-type resin, a polysulfone, a polyarylate, a polyamideimide, a polyetherimide, a thermoplastic polyimide, etc., or those composite base materials can be mentioned. As the plastic substrate 10, a thin flexible film having a thickness of about 5 μm to 300 μm can be used, and a panel on which a thin film transistor is formed can be made flexible.

  First, the inorganic adhesion layer 11 is formed on the prepared plastic substrate 10 (see FIG. 2A). The inorganic adhesion layer 11 needs to be formed at least in the region where the TFT is formed, but may or may not be formed in other regions, and is formed on the entire surface of the plastic substrate 10. Also good. The inorganic adhesion layer 11 is formed of any material selected from the group consisting of chromium, titanium, aluminum, silicon, chromium oxide, titanium oxide, aluminum oxide, silicon nitride, and silicon oxynitride. Among these, the metal-based inorganic adhesion layer made of chromium, titanium, aluminum, silicon, or the like can effectively prevent the plastic substrate and the buffer layer from being peeled by the thermal history during the TFT manufacturing process. In addition, the inorganic adhesion layer made of a metal oxide material such as chromium oxide or titanium oxide produces an adhesion effect because the metal atoms contained in the composition interact with the plastic substrate 10, and the thermal history during the TFT manufacturing process. Prevents peeling due to.

  Although the range of the thickness of the inorganic adhesion layer 11 is slightly different depending on the material constituting the layer, it is usually preferably in the range of 1 to 200 nm, and more preferably in the range of 3 to 50 nm. In the case of a metal-based inorganic adhesion layer made of chromium, titanium, aluminum, or silicon, it is more preferably within a range of 3 to 10 nm, and chromium oxide, titanium oxide, aluminum oxide, silicon nitride, or acid In the case of a compound-based inorganic adhesion layer made of silicon nitride, it is more preferably in the range of 5 to 50 nm.

  The inorganic adhesion layer 11 can be formed by various methods such as a DC sputtering method, an RF magnetron sputtering method, and a plasma CVD method, but in practice, a preferred method according to the material constituting the layer is adopted. Is done. Usually, a DC sputtering method, an RF magnetron sputtering method, or the like is preferably used.

  Next, as shown in FIG. 2A, the buffer layer 12 is formed on the inorganic adhesion layer 11. The buffer layer 12 needs to be formed at least in the region where the TFT is formed, but may or may not be formed in other regions, or may be formed on the entire surface of the plastic substrate 10. Good. The buffer layer 12 is usually made of silicon oxide. Since the buffer layer 12 acts to prevent impurity ions contained in the plastic substrate or the inorganic adhesion layer from diffusing into the semiconductor thin film, it is possible to prevent deterioration of the characteristics of the semiconductor thin film.

  The thickness of the buffer layer 12 is usually preferably in the range of 100 to 3000 nm, and more preferably in the range of 100 to 1500 nm from the viewpoint of film stress. The buffer layer 12 can be formed by an RF magnetron sputtering method in which silicon is sputtered in an oxygen atmosphere, a plasma CVD method, or the like.

Next, as shown in FIG. 2B, a non-doped amorphous silicon thin film 21 a is formed on the buffer layer 12. The amorphous silicon thin film 21a can be formed by various methods such as an RF magnetron sputtering method and a CVD method. For example, when an amorphous silicon thin film is formed by the RF magnetron sputtering method, for example, the film is formed at a thickness of, for example, 50 nm under a film forming temperature: room temperature, a film forming pressure: 1.0 Pa, and a gas: argon film forming condition. I can make a film. In addition, even when an amorphous silicon thin film is formed by the CVD method, the film can be formed at a film forming temperature of about 25 ° C. However, since SiH ₄ is used as a source gas, a dehydrogenation process at about 400 ° C. is performed after the film formation. (About 1 hour in a vacuum) is required. The inorganic adhesion layer 11 is effective against the heat applied during the dehydrogenation treatment, and can prevent the interface peeling between the plastic substrate 10 and the buffer layer 12 based on the heat during the dehydrogenation treatment.

Next, as shown in FIG. 2C, laser annealing 22 is performed to crystallize the amorphous silicon thin film 21a to change it to a low resistance polysilicon thin film 21p. The laser annealing 22 is a crystallization means for crystallizing the amorphous silicon thin film 21a into a polysilicon thin film 21p (polycrystalline silicon thin film), and is performed by various lasers such as an XeCl excimer laser, a CW (Continuous Wave) laser, or the like. Can do. For example, when crystallization is performed using a XeCl excimer laser, as an example, it can be performed under conditions of a pulse width: 30 nsec, an energy density: 400 mJ / cm ² , and room temperature. The inorganic adhesion layer 11 has a remarkable effect on the heat of laser annealing applied in this step, and can prevent the interface peeling between the plastic substrate 10 and the buffer layer 12 based on the heat of laser annealing.

  Next, as shown in FIG. 2D, a resist film 23 is formed on the polysilicon thin film 21p, and then the resist film 23 is patterned. For the resist film 23, for example, a positive photoresist is preferably used. The resist film 23 is formed by applying a resist to the entire surface by means of a spinner or the like and drying and curing it. Said inorganic adhesion layer 11 is effective also with respect to the heat | fever of the drying process added at this process, and can prevent the interface peeling of the plastic substrate 10 and the buffer layer 12 based on the heat | fever of this drying process.

After patterning the resist film, 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 doping level of 2 × 10 ¹⁵ / cm ² . By such ion implantation, a source-side diffusion film 13s and a drain-side diffusion film 13d are formed in the polysilicon thin film, and a semiconductor channel film 13c is formed between the films 13s and 13d.

Next, as shown in FIG. 2E, 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, and as an example, it can be performed under conditions of a pulse width: 30 nsec, an energy density: 250 mJ / cm ² , and room temperature. The inorganic adhesion layer 11 is also effective against the heat of the energy beam applied in this step, and can prevent interface peeling between the plastic substrate 10 and the buffer layer 12 based on the heat of the energy beam.

  In addition, after the above activation treatment, an oxygen plasma treatment for reducing the defects of the polysilicon thin film is usually performed. For example, the oxygen plasma treatment is performed under the conditions of RF 100 W, 1 Torr, and 150 ° C., and thereafter, the drying treatment is performed under the condition of 120 ° C. The above-mentioned inorganic adhesion layer 11 is also effective against the heat at the time of oxygen plasma generation applied in this step and the heat at the time of subsequent drying, and the interface peeling between the plastic substrate 10 and the buffer layer 12 based on these heats. Can be prevented.

Next, as shown in FIG. 3F, dry etching is performed to form islands. As the etching gas, SF ₆ or the like can be used. After the island is formed, washing with water, and washing and drying under a condition of 120 ° C. are performed. The inorganic adhesion layer 11 is also effective against the heat during drying applied in this step, and can prevent interface peeling between the plastic substrate 10 and the buffer layer 12 based on the heat.

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

  Next, as shown in FIG. 3H, contact holes 26 and 26 are formed by selectively etching the gate insulating film 14 on the source side diffusion film 13s and the drain side diffusion film 13d using a mask. To do. As the etching at this time, for example, wet etching using a 2% HF solution can be applied. Thereafter, a washing process and a drying process are performed. Said inorganic adhesion layer 11 is effective also with respect to the heat | fever added by this drying process, and can prevent the interface peeling of the plastic substrate 10 and the buffer layer 12 based on the heat | fever.

  Next, as shown in FIG. 3I, an aluminum (Al) film having a thickness of, for example, 200 nm is deposited on the entire surface, and then patterned by wet etching to form a source electrode 15s, a drain electrode 15d, and a gate electrode 15g. To do. The electrode material may be Cu or other conductive material, and may be formed by other film forming processes such as sputtering. The inorganic adhesion layer 11 is also effective against heat during the cleaning and drying process applied after wet etching in this process, and can prevent interface peeling between the plastic substrate 10 and the buffer layer 12 based on the heat. .

  Finally, after forming a protective layer (not shown) made of silicon oxide, as shown in FIG. 3J, treatment with hydrogen plasma 27 is performed to terminate silicon defects in the polycrystalline polysilicon thin film. For example, there is a method of eliminating dangling bonds on the silicon surface and eliminating a leak path at the interface between polysilicon and the gate insulating film by hydrogen plasma treatment. Thus, the thin film transistor of one embodiment illustrated in FIG. 3J is manufactured. The inorganic adhesion layer 11 is also effective against heat applied during the hydrogen plasma treatment in this step, and can prevent interface peeling between the plastic substrate 10 and the buffer layer 12 based on the heat.

  As described above, according to the present invention, since the inorganic adhesion layer is formed, even when heat is applied in a plurality of steps at the time of manufacturing the thin film transistor, the interface separation between the plastic substrate and the buffer layer is performed. Can be prevented. The thin-film transistor mounting panel of the present invention thus manufactured has a form in which TFTs are formed on a flexible plastic substrate. Therefore, a flexible display can be designed by combining with an organic EL element, for example. .

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In addition, this invention is not limited to a following example.

Example 1
Using polyethylene naphthalate (PEN) having a thickness of 0.2 mm and a thickness of 100 mm × 100 mm as a plastic substrate, an aluminum film as an inorganic adhesion layer is formed on the plastic substrate by a DC sputtering method (deposition pressure 0.2 Pa (argon), After forming a thickness of 5 nm by an input power of 1 kW and a film formation time of 10 seconds, silicon oxide as a buffer layer was further formed by RF magnetron sputtering (film formation pressure 0.3 Pa (argon: oxygen = 3: 1), input power 2 kW. And a film formation time of 2 hours). Further, amorphous silicon was formed to a thickness of 50 nm by RF magnetron sputtering (film formation temperature: room temperature, film formation pressure: 1.0 Pa (argon)).

After that, a TFT-mounted panel was manufactured based on the conditions exemplified in the description column of the steps of FIGS. 2B to 3J described above. In addition, in this TFT mounting panel manufacturing process, the following thermal history was added specifically. First, in the amorphous silicon thin film forming step in FIG. 2B, after the amorphous silicon thin film was formed, a dehydrogenation treatment at 400 ° C. (for 1 hour in a vacuum) was performed. In the next crystallization step of FIG. 2C, laser annealing using a XeCl excimer laser was performed under the conditions of an energy density of 400 mJ / cm ² , a pulse width of 30 nsec, room temperature, and the number of irradiations of 20 times. In the patterning and ion implantation process of FIG. 2D, a drying process at 120 ° C. is performed after the patterning, and then phosphorus is doped at a doping level of 2 × 10 ¹⁵ / cm ^{2 at} an implantation voltage of 10 keV and room temperature. Ion implantation. In the activation step of FIG. 2E, activation treatment was performed using a XeCl excimer laser under conditions of a pulse width of 30 nsec, an energy density of 250 mJ / cm ² , and room temperature. After the activation treatment, an oxygen plasma treatment was performed under the conditions of RF 100 W, 1 Torr, and 150 ° C., and then a drying treatment was performed under the condition of 120 ° C. Next, in the island formation step of FIG. 3 (F), a drying process at 120 ° C. is performed. Thereafter, in the contact hole formation step of FIG. 3 (H), a drying process at 120 ° C. is performed, and further, FIG. In the wet etching step, heat treatment at 120 ° C. was performed, and in the hydrogen plasma treatment step in FIG. 3J, treatment at RF 200 W, 1 Torr, and 150 ° C. was performed. A TFT-mounted panel was manufactured through each of these thermal histories.

(Examples 2-9)
A thin film transistor mounting panel was manufactured in the same manner as in Example 1 except that the kind of the inorganic adhesion layer, its film thickness, or the plastic substrate was changed as shown in Table 1.

(Comparative Examples 1 and 2)
A thin film transistor mounting panel was manufactured in the same manner as in Example 1 except that the inorganic adhesion layer was not formed.

(Adhesion evaluation)
Adhesion (peeling resistance) was determined by using a scotch mending tape (manufactured by Sumitomo 3M, length 30 m x width 12 mm) and attaching a part of the tape (length 30 mm) onto the fabricated TFT. It evaluated by the tape peeling test method which peels and evaluates the presence or absence of peeling. The adhesion results are shown in Table 1. In the evaluation of adhesion, ◎ indicates that no peeling or cracking has occurred, and ◯ indicates that there is little discoloration at the edge portion, etc. but there is no practical problem, and repeats the peeling test several times. Although the peeling occurred, the practically usable one was marked as Δ, and the element portion was peeled and difficult to use was marked as x. As can be seen from the results in Table 1, it is preferable to form a metal-based inorganic adhesion layer as the preferable inorganic adhesion layer, and particularly preferably Al and Cr.

It is a schematic cross section which shows an example of the TFT element part of the thin-film transistor mounting panel of this invention. It is explanatory drawing which shows the manufacturing process of the thin-film transistor mounting panel of this invention. It is explanatory drawing which shows the manufacturing process of the thin-film transistor mounting panel of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 TFT element part 10 Plastic substrate 11 Inorganic adhesion layer 12 Buffer layer 13 Polysilicon semiconductor thin film 13s Source side diffused film 13c Semiconductor channel film 13d Drain side diffused film 14 Gate insulating film 15s Source electrode 15g Gate electrode 15d Drain electrode 21a Amorphous silicon thin film 21p polysilicon thin film 22 laser annealing 23 resist film 24 ion implantation 25 energy beam 26 contact hole 27 hydrogen plasma

Claims (5)

  A thin film transistor mounting panel in which a polysilicon thin film is formed on a plastic substrate through a buffer layer, and an inorganic adhesion layer is formed between the plastic substrate and the buffer layer. Mounted panel.   2. The inorganic adhesion layer is made of any one selected from the group consisting of chromium, titanium, aluminum, silicon, chromium oxide, titanium oxide, aluminum oxide, silicon nitride, and silicon oxynitride. Thin film transistor mounted panel.   3. The thin film transistor mounting panel according to claim 1, wherein the buffer layer is silicon oxide.   Forming an inorganic adhesion layer on a plastic substrate; forming a buffer layer on the inorganic adhesion layer; forming an amorphous silicon thin film on the buffer layer; and laser annealing the amorphous silicon thin film. Manufacturing a thin film transistor mounting panel, comprising: forming a polysilicon thin film; and adding impurity ions to a predetermined region of the polysilicon thin film and then thermally activating by laser annealing to form an impurity diffusion region Method.   The inorganic adhesion layer is made of any one selected from the group consisting of chromium, titanium, aluminum, silicon, chromium oxide, titanium oxide, aluminum oxide, silicon nitride, and silicon oxynitride. Manufacturing method of thin film transistor mounting panel.

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