JPWO2013061383A1 - Thin film semiconductor device and manufacturing method thereof - Google Patents

Abstract

The method of manufacturing a thin film semiconductor device (10) according to the present invention includes a first step of preparing a substrate (1), a second step of forming a gate electrode (2) on the substrate (1), and a gate electrode (2 ) A third step of forming a gate insulating film (3) as a first insulating film thereon, and an amorphous semiconductor thin film (4a) to be a channel layer (4) is formed on the gate insulating film (3). A fourth step, a fifth step of forming a channel protective film (5) as a second insulating film on the amorphous semiconductor thin film (4a), and irradiating the channel protective film (5) with laser light. The sixth step of increasing the transmittance of the channel protective film (5) and the seventh step of forming the source electrode (7S) and the drain electrode (7D) above the channel layer (4) are included.

Description

  The present invention relates to a thin film semiconductor device and a manufacturing method thereof, and more particularly to a channel protection type thin film transistor and a manufacturing method thereof.

  In recent years, an organic EL display using an organic material EL (Electro Luminescence) as one of the next generation flat panel displays replacing the liquid crystal display has been attracting attention. In an active matrix display device such as an organic EL display, a thin film semiconductor device called a thin film transistor (TFT) is used.

  In particular, an organic EL display is a current-driven display device unlike a voltage-driven liquid crystal display, and development of a thin film transistor having excellent on / off characteristics as a drive circuit of an active matrix display device has been urgently developed. A thin film transistor has a structure in which a gate electrode, a semiconductor layer (channel layer), a source electrode, and a drain electrode are formed on a substrate, and a silicon thin film is generally used for the channel layer.

  In addition, display devices are required to have a large screen and a low cost, and as a thin film transistor that can be easily reduced in cost, generally a bottom gate type in which a gate electrode is formed on the substrate side from a channel layer. The thin film transistor is used.

  Bottom-gate thin film transistors are roughly classified into two types: a channel etching type thin film transistor in which a channel layer is etched, and a channel protection type (etching stopper type) thin film transistor that protects the channel layer from an etching process.

  A channel etching type thin film transistor has an advantage that the number of photolithography steps can be reduced and a manufacturing cost can be reduced as compared with a channel protection type thin film transistor.

  On the other hand, the channel protective thin film transistor can prevent damage to the channel layer due to the etching process, and can suppress variation in characteristics in the substrate surface. In addition, a channel protection type thin film transistor is advantageous for high definition because a channel layer can be thinned and a parasitic resistance component can be reduced to improve on-state characteristics.

  Therefore, the channel protection type thin film transistor is suitable for a driving transistor in a current driving type organic EL display device using an organic EL element, for example. Even if the manufacturing cost is increased as compared with the channel etching type thin film transistor, Attempts have been made to employ it in pixel circuits of EL display devices.

  For example, Patent Document 1 discloses a channel protection type TFT using a microcrystalline semiconductor thin film as a channel layer, and describes forming a channel protection layer on the channel layer via a buffer layer.

JP 2009-76894 A

  However, in a channel protection type thin film transistor, a positive fixed charge is present in the channel protection layer, so that a back channel is formed in the channel layer due to this fixed charge, resulting in an increase in leakage current and a deterioration in the off characteristics of the thin film transistor. There is a problem of doing. In particular, when the channel protective layer is formed by applying an organic material, the channel protective layer contains a larger amount of positive fixed charges than the channel protective layer made of an inorganic material. It gets worse.

  In a channel protective thin film transistor, trap levels exist in the channel protective layer due to impurities contained in the channel protective layer, and carriers are easily trapped by this trap level. As a result, the threshold voltage of the thin film transistor is reduced. There is also a problem that the reliability of the thin film transistor is deteriorated. In particular, a channel protective layer made of a coating-type organic material has more trap levels in the channel protective layer than a channel protective layer made of an inorganic material. Sexually worsens.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a thin film semiconductor device excellent in off characteristics and reliability in a channel protection type thin film transistor and a method for manufacturing the same.

  In order to achieve the above object, a method of manufacturing a thin film semiconductor device according to one embodiment of the present invention includes a first step of preparing a substrate, a second step of forming a gate electrode on the substrate, A third step of forming a first insulating film, a fourth step of forming a semiconductor thin film serving as a channel layer on the first insulating film, and a fifth step of forming a second insulating film on the semiconductor thin film. And a sixth step of increasing the transmittance of the second insulating film by irradiating the second insulating film with light, and a seventh step of forming a source electrode and a drain electrode above the channel layer, It is characterized by including.

  The thin film semiconductor device according to one embodiment of the present invention is formed over a substrate, a gate electrode formed over the substrate, a first insulating film formed over the gate electrode, and the first insulating film. A crystalline semiconductor thin film, a source electrode and a drain electrode formed above the crystalline semiconductor thin film, and a second insulating film formed on the crystalline semiconductor thin film, The second insulating film is formed by irradiating the precursor of the second insulating film with the light beam, and the transmittance of the second insulating film with respect to the light beam is higher after the light beam irradiation and before the light beam irradiation. It is characterized by that.

  According to the present invention, a thin film semiconductor device having excellent off characteristics and reliability can be realized.

FIG. 1 is a cross-sectional view showing a configuration of a thin film semiconductor device according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view for explaining the method of manufacturing the thin film semiconductor device according to the first embodiment of the invention. FIG. 3A is a cross-sectional view showing a configuration of a conventional thin film semiconductor device. FIG. 3B is a cross-sectional view showing a configuration of a conventional thin film semiconductor device. FIG. 4 is a diagram showing current-voltage characteristics of a conventional thin film semiconductor device. FIG. 5 is a diagram showing an IR spectrum of the silicon oxide film. FIG. 6 is a diagram showing an IR spectrum of the organic film. FIG. 7 is a diagram showing an IR spectrum of the organic film. FIG. 8A is an enlarged view of the IR spectrum of the organic film in FIG. FIG. 8B is an enlarged view of the IR spectrum of the organic film in FIG. FIG. 9A is a diagram (wavelength is on the horizontal axis) showing the dependency of the refractive index on the wavelength and temperature when the organic film of material A is heat-treated. FIG. 9B is a diagram (wavelength is on the horizontal axis) showing the dependency of the refractive index on the wavelength and temperature when the organic film of material A is heat-treated. FIG. 10A is a diagram (wavelength is on the horizontal axis) showing the dependency of the wavelength and temperature on the extinction coefficient when the organic film of the material A is heat-treated. FIG. 10B is a diagram (wavelength is on the horizontal axis) showing the dependency of the wavelength and temperature on the extinction coefficient when the organic film of material A is heat-treated. FIG. 11A is a diagram (wavelength is on the horizontal axis) showing the dependency of the absorption coefficient on wavelength and temperature when the organic film of material A is heat-treated. FIG. 11B is a diagram (wavelength is on the horizontal axis) showing the dependency of the absorption coefficient on the wavelength and temperature when the organic film of material A is heat-treated. FIG. 12A is a diagram (wavelength is on the horizontal axis) showing the dependency of the absorption coefficient on the wavelength and temperature when the organic film of the material B is heat-treated. FIG. 12B is a diagram (wavelength is on the horizontal axis) showing the dependency of the absorption coefficient on wavelength and temperature when the organic film of material B is heat-treated. FIG. 13A is a diagram (wavelength is on the horizontal axis) showing the dependency of the absorption coefficient on wavelength and temperature when the organic film of material C is heat-treated. FIG. 13B is a diagram showing the dependence of the absorption coefficient on the wavelength and temperature when the organic film of material C is heat-treated (the horizontal axis is temperature). FIG. 14 is a diagram illustrating the relationship between the organic film absorption coefficient and the organic film transmittance with respect to the organic film thickness. FIG. 15A is a figure for demonstrating the effect of the thin film semiconductor device based on the 1st Embodiment of this invention. FIG. 15B is a diagram for explaining the function and effect of the thin film semiconductor device according to the first embodiment of the present invention. FIG. 16 is a diagram showing the change in the absorptance of the amorphous semiconductor thin film when the thickness of the channel protective film is changed. FIG. 17A is a cross-sectional view showing the configuration of the thin film semiconductor device according to the first embodiment when an interface layer is formed. FIG. 17B is a cross-sectional view showing the configuration of another thin film semiconductor device according to the first embodiment when an interface layer is formed. 18A is a cross-sectional TEM image around the interface layer of the thin film semiconductor device shown in FIG. 17A. FIG. 18B is a schematic diagram for explaining a cross-sectional structure of a region B surrounded by a broken line in FIG. 18A. FIG. 19 is a diagram showing the concentration distribution of carbon and sulfur contained in the film constituting the thin film semiconductor device shown in FIG. 17A. FIG. 20 is a cross-sectional view for explaining the method for manufacturing the thin film semiconductor device according to the second embodiment of the present invention. FIG. 21 is a cross-sectional view for explaining the method for manufacturing the thin film semiconductor device according to the third embodiment of the present invention. FIG. 22 is a partially cutaway perspective view of an organic EL display device according to a fourth embodiment of the present invention. FIG. 23 is a diagram showing a circuit configuration of a pixel in the display device using the thin film semiconductor device according to the first embodiment of the present invention.

  A method for manufacturing a thin film semiconductor device according to an aspect of the present invention includes a first step of preparing a substrate, a second step of forming a gate electrode on the substrate, and a first insulating film on the gate electrode. A third step, a fourth step of forming a semiconductor thin film serving as a channel layer on the first insulating film, a fifth step of forming a second insulating film on the semiconductor thin film, and A sixth step of increasing the transmittance of the second insulating film by irradiating light; and a seventh step of forming a source electrode and a drain electrode above the channel layer.

  According to this aspect, the transmittance of the second insulating film is increased by irradiating the second insulating film formed on the semiconductor thin film with light. As a result, the second insulating film can be made inorganic, so that the fixed charge of the second insulating film can be reduced, the formation of the back channel can be suppressed, and a thin film semiconductor device having excellent off characteristics can be realized. Further, by making the second insulating film inorganic, the trap level of the second insulating film can be reduced, carrier traps can be suppressed, and the threshold voltage shift can be suppressed. Therefore, a highly reliable thin film semiconductor device can be obtained. realizable.

  In the method of manufacturing a thin film semiconductor device according to one aspect of the present invention, in the fifth step, the second insulating film made of an organic material having a light transmittance of less than 37% is formed, and the sixth step In the above, it is preferable that the transmittance of the second insulating film is 37% or more by irradiation with the light beam.

  According to this aspect, since the transmittance of the second insulating film is 37% or less before irradiation with light, the light is absorbed by the second insulating film and generates heat. Thereby, the second insulating film can be easily made transparent. Moreover, since the transmittance of the second insulating film is 37% or more after the light irradiation, the light passes through the second insulating film and is absorbed by the semiconductor thin film to generate heat. Thereby, the semiconductor thin film can be easily heat-treated, and the second insulating film can be made transparent by heat propagation. By these actions, a thin film semiconductor device having excellent off characteristics and reliability can be realized.

  In the method of manufacturing a thin film semiconductor device according to an aspect of the present invention, the amorphous semiconductor thin film is formed in the fourth step, and the light beam is emitted from above the second insulating film in the sixth step. It is preferable to crystallize the semiconductor thin film below the second insulating film by irradiating.

  According to this aspect, the transmittance of the second insulating film can be increased and the semiconductor thin film can be crystallized by a single light beam scan. As a result, the transmittance of the second insulating film can be increased without increasing the number of steps.

  In the method of manufacturing a thin film semiconductor device according to one aspect of the present invention, in the fourth step, the amorphous semiconductor thin film is formed, and further, between the sixth step and the seventh step. A step of crystallizing the semiconductor thin film may be included. Alternatively, in the fourth step, the crystallized semiconductor thin film may be formed.

  According to this aspect, since the step of increasing the transmittance of the second insulating film and the step of crystallizing the semiconductor thin film are performed separately, it is possible to irradiate the light with each desired condition. Therefore, the transmittance of the second insulating film can be reliably increased, and the semiconductor thin film can be reliably crystallized.

  In the method for manufacturing a thin film semiconductor device according to one embodiment of the present invention, the product of the absorption coefficient of the second insulating film and the film thickness of the second insulating film is greater than 1 before the irradiation with the light beam. can do. In addition, the product of the absorption coefficient of the second insulating film and the film thickness of the second insulating film after the irradiation of the light beam may be 1 or less.

  In the method for manufacturing a thin film semiconductor device according to one embodiment of the present invention, in the sixth step, the second insulating film may be mineralized by irradiation with the light beam. In this case, the mineralization may be caused by a light reaction or a thermal reaction proceeding in the second insulating film by the light beam.

  The thin film semiconductor device according to one embodiment of the present invention is formed over a substrate, a gate electrode formed over the substrate, a first insulating film formed over the gate electrode, and the first insulating film. A crystalline semiconductor thin film, a source electrode and a drain electrode formed above the crystalline semiconductor thin film, and a second insulating film formed on the crystalline semiconductor thin film, The second insulating film is formed by irradiating the precursor of the second insulating film with the light beam, and the transmittance of the second insulating film with respect to the light beam is higher after the light beam irradiation and before the light beam irradiation. .

  According to this aspect, the transmittance of the second insulating film can be increased by irradiating the second insulating film with light on the semiconductor thin film. As a result, the second insulating film can be made inorganic, so that the fixed charge of the second insulating film can be reduced, the formation of the back channel can be suppressed, and a thin film semiconductor device having excellent off characteristics can be realized. Further, by making the second insulating film inorganic, the trap level of the second insulating film can be reduced, carrier traps can be suppressed, and the threshold voltage shift can be suppressed. Therefore, a highly reliable thin film semiconductor device can be obtained. realizable.

  In the thin film semiconductor device according to one embodiment of the present invention, the transmittance of the second insulating film with respect to the light beam is less than 37% before irradiation with the light beam and is 37% or more after irradiation with the light beam. , And can be.

  In the thin film semiconductor device according to one embodiment of the present invention, the precursor is made of an organic material, and the second insulating film is made of the organic material made inorganic by irradiation with the light beam. Can do.

  In the thin film semiconductor device according to one embodiment of the present invention, a product of an absorption coefficient of the second insulating film and a film thickness of the second insulating film before irradiation with the light beam may be greater than 1. it can.

  In the thin film semiconductor device according to one embodiment of the present invention, the product of the absorption coefficient of the second insulating film and the film thickness of the second insulating film after the light irradiation is 1 or less. Can do.

The thin film semiconductor device according to one embodiment of the present invention further includes a carbon-containing interface layer formed between the crystalline semiconductor thin film and the second insulating film, and the interface layer includes The concentration of carbon contained is preferably 50 times or more the concentration of carbon as an impurity contained in the crystalline semiconductor thin film. In this case, the concentration of carbon contained in the interface layer is preferably 5 × 10 ²⁰ (atoms / cm ³ ) or more.

In the thin film semiconductor device according to one embodiment of the present invention, the interface layer may contain sulfur. In this case, the concentration of sulfur contained in the interface layer is preferably 100 times or more the concentration of sulfur as an impurity contained in the crystalline semiconductor thin film. Or it is preferable that the density | concentration of the sulfur contained in the said interface layer is 5 * 10 < ¹⁹ > (atoms / cm < ³ >) or more.

In the thin film semiconductor device according to one embodiment of the present invention, the specific resistance of the interface layer is preferably 2 × 10 ⁶ (Ω · cm) or more.

  In the thin film semiconductor device according to one embodiment of the present invention, the interface layer can have a thickness of 1 nm to 5 nm.

  Hereinafter, a thin film semiconductor device and a manufacturing method thereof according to embodiments of the present invention will be described with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. That is, the present invention is specified only by the claims. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present invention are not necessarily required to achieve the object of the present invention. It will be described as constituting a preferred form. Moreover, in each drawing, the same code | symbol is attached | subjected about the element showing substantially the same structure, operation | movement, and an effect.

(First embodiment)
First, the configuration of the thin film semiconductor device 10 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing a configuration of a thin film semiconductor device 10 according to the first embodiment of the present invention.

  As shown in FIG. 1, a thin film semiconductor device 10 according to a first embodiment of the present invention is a channel protection type bottom gate type thin film transistor, which is sequentially formed on a substrate 1 and above the substrate 1. , A gate electrode 2, a gate insulating film (first insulating film) 3, a channel layer (semiconductor thin film) 4, and a channel protective film (second insulating film) 5, and the channel layer 4 sandwiching the channel protective film 5. And a pair of source electrode 7S and drain electrode 7D formed on the contact layer 6.

  Hereinafter, each component of the thin film semiconductor device 10 according to the present embodiment will be described in detail.

The substrate 1 is a glass substrate made of a glass material such as quartz glass, non-alkali glass, and high heat resistant glass. In order to prevent impurities such as sodium and phosphorus contained in the glass substrate from entering the channel layer 4, silicon nitride (SiN _x ), silicon oxide (SiO _y ) or silicon oxynitride film (SiO 2) is formed on the surface. A substrate on which an undercoat layer made of SiO _y N _x ) or the like is formed may be used. In addition, the undercoat layer may play a role of reducing the influence of heat on the substrate 1 in a high-temperature heat treatment process such as laser annealing. The film thickness of the undercoat layer can be, for example, about 100 nm to 2000 nm.

  The gate electrode 2 is formed in a predetermined shape above the substrate 1. The gate electrode 2 has a single-layer structure or a multilayer structure such as a conductive material that can withstand the melting point temperature of silicon or an alloy thereof. For example, molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W) Ta (tantalum), Nb (niobium), Ni (nickel), titanium (Ti), chromium (Cr), molybdenum tungsten (MoW), or the like can be used. The gate electrode 2 is formed by forming a gate metal film made of these materials on the substrate 1 and patterning it into a predetermined shape. The film thickness of the gate electrode 2 is preferably 30 nm or more and 300 nm or less, and more preferably 50 nm or more and 100 nm or less. This is because if the film thickness of the gate electrode 2 is thin, the transmittance of the gate electrode 2 increases, and the reflection of the laser light tends to decrease. On the other hand, when the thickness of the gate electrode 2 is large, the coverage of the gate insulating film 3 is lowered, and in particular, the characteristics of the thin film transistor are deteriorated such that the gate insulating film 3 is disconnected at the end of the gate electrode 2. This is because it becomes easier.

The gate insulating film 3 is a first insulating film formed on the gate electrode 2 and is formed on the substrate 1 and the gate electrode 2 so as to cover the gate electrode 2 on the substrate 1. The gate insulating film 3 can be formed using, for example, silicon oxide, silicon nitride, silicon oxynitride film, aluminum oxide (AlO _z ), tantalum oxide (TaO _w ), or a laminated film thereof.

  In this embodiment, since a crystalline silicon thin film is used as the channel layer 4, it is preferable to use silicon oxide as the gate insulating film 3. This is because in order to maintain good threshold voltage characteristics in the TFT, it is preferable to make the interface state between the channel layer 4 and the gate insulating film 3 good, and silicon oxide is suitable for this. .

  The channel layer 4 includes a crystalline semiconductor thin film formed on the gate insulating film 3, and has a channel region that is a region in which carrier movement is controlled by the voltage of the gate electrode 2. In the present embodiment, at least the channel region of the channel layer 4 is a crystalline silicon thin film made of a polycrystalline silicon thin film, and the amorphous silicon thin film (amorphous silicon film) as the precursor is made of amorphous silicon. It is a crystallized region formed by polycrystallizing (including microcrystallization) by irradiating at least a part with a laser. The channel layer 4 may be a crystalline silicon thin film having a mixed crystal structure of amorphous silicon and crystalline silicon. Further, the average grain size of the crystals contained in the channel layer 4 is, for example, not less than 10 nm and not more than 1 μm.

  In the present embodiment, the crystallization of the channel layer 4 is performed simultaneously with the film reforming step of the channel protective film 5, and scanning with laser light from above the organic film 5 a that is a precursor of the channel protective film 5. The laser light is irradiated to the region where the organic film 5a is not formed and the region where the organic film 5a is formed in the amorphous silicon thin film. As a result, the amorphous silicon thin film including the region below the organic film 5a is crystallized to become a crystalline silicon thin film.

  The channel protective film 5 is a second insulating film formed on the channel layer 4 and is a protective film that protects the channel region of the channel layer 4. That is, the channel protective film 5 functions as a channel etching stopper (CES) layer for preventing the channel layer 4 from being etched during the etching process when forming the pair of contact layers 6. Since the channel protective film 5 has an insulating property, the pair of contact layers 6 are not electrically connected to each other.

  The channel protective film 5 is formed by irradiating the organic film applied on the channel layer 4 with laser light. The channel protective film 5 is a transparent film in which an opaque organic film that is a precursor (channel protective film 5 before laser light irradiation) is made transparent by laser irradiation, and the transmittance of the channel protective film 5 to the laser light. Is higher after laser light irradiation than before laser light irradiation. That is, the transmittance of the channel protective film 5 after laser light irradiation is higher than the transmittance of the channel protective film 5 before laser irradiation.

  In the channel protective film 5, the transmittance of the organic film (precursor) with respect to laser light is less than 37%. That is, the transmittance of the channel protective film 5 with respect to the laser light is less than 37% before the laser light irradiation. At this time, the product of the absorption coefficient of the channel protective film 5 and the film thickness of the channel protective film 5 is greater than 1 before the laser light irradiation.

  On the other hand, the organic film (precursor) is made transparent by irradiation with laser light, and the transmittance with respect to the laser light becomes 37% or more. That is, the transmittance of the channel protective film 5 with respect to the laser light becomes 37% or more after the laser light irradiation. At this time, the product of the absorption coefficient of the channel protective film 5 and the film thickness of the channel protective film 5 is 1 or less after the laser light irradiation.

  The transmittance of the channel protective film 5 is determined by the thickness of the organic film and the absorption coefficient of the organic film. The absorption coefficient of the organic film is determined by the wavelength of the laser light and the heating temperature of the organic film. Details will be described later.

  Furthermore, the organic film (precursor) is modified into an inorganic film containing an inorganic component such as a silicon oxide component or a silicon nitride component as a main component by irradiation with laser light. That is, the channel protective film 5 is a transparent film obtained by irradiating a laser beam and transparentizing an organic film as a precursor, and an inorganic film obtained by making it inorganic.

  Here, the organic film which is a precursor of the channel protective film 5 is made of an organic material mainly containing an organic material containing silicon, oxygen, and carbon. For example, by patterning and solidifying a photosensitive coating type organic material. Can be formed.

  The organic material for forming this organic film (precursor) is composed of, for example, an organic resin material, a surfactant, a solvent, and a photosensitizer. As the organic resin material, a photosensitive or non-photosensitive organic resin material composed of one or more kinds selected from polyimide, acrylic, polyamide, polyimide amide, resist, benzocyclobutene, and the like can be used. As the surfactant, a surfactant made of a silicon compound such as siloxane can be used. As the solvent, an organic solvent such as propylene glycol monomethyl ether acetate or 1,4-dioxane can be used. As the photosensitizer, a positive photosensitizer such as naphthoquinone diazite can be used. Note that the photosensitizer contains carbon and sulfur.

  The pair of contact layers 6 are made of an amorphous semiconductor layer containing impurities at a high concentration or a polycrystalline semiconductor layer containing impurities at a high concentration, and a part of the contact layers 6 is located above the channel layer 4 via a channel protective film 5. The other part is formed on and in contact with the channel layer 4. The pair of contact layers 6 are disposed on the channel protective film 5 so as to face each other at a predetermined interval.

  Each of the pair of contact layers 6 is formed so as to straddle from the upper surface end of the channel protective film 5 to the upper surface of the channel layer 4, and the upper surface and side surfaces of the channel protective film 5 and the upper surface of the channel layer 4. It is formed so as to cover. More specifically, the two contact layers 6 are provided above both end portions of the channel layer 4, and the channel layer 4 formed on the upper and side surfaces of the end portion of the channel protective film 5 and the side surface of the channel protective film 5. It is formed on the upper surface.

The pair of contact layers 6 are, for example, n-type semiconductor layers in which amorphous silicon is doped with phosphorus (P) as an impurity, and an n ⁺ layer containing a high-concentration impurity of 1 × 10 ¹⁹ (atm / cm ³ ) or more. It is. The film thickness of each contact layer 6 can be set to, for example, 5 nm to 100 nm.

  The pair of source electrode 7S and drain electrode 7D are formed in the same layer above the channel region (crystallization region) of the channel layer 4 via the channel protective film 5. In this embodiment, a pair of contacts Oppositely arranged on the layer 6 at a predetermined interval. That is, the source electrode 7S is formed above one end portion of the channel layer 4 via the contact layer 6, and the drain electrode 7D is formed on the other end portion of the channel layer 4 via the contact layer 6. Is formed above.

  The source electrode 7S and the drain electrode 7D can each have a single layer structure or a multilayer structure made of a conductive material or an alloy thereof, for example, aluminum (Al), tantalum (Ta), molybdenum (Mo), tungsten (W), silver (Ag), copper (Cu), titanium (Ti), or chromium (Cr). Further, the source electrode 7S and the drain electrode 7D may have a three-layer structure of MoW / Al / MoW. The film thickness of the source electrode 7S and the drain electrode 7D can be set to, for example, about 100 nm to 500 nm.

  Next, a method for manufacturing the thin film semiconductor device 10 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view schematically showing the configuration of each step in the method for manufacturing a thin film semiconductor device according to the first embodiment of the present invention.

  The manufacturing method of the thin film semiconductor device according to the present embodiment includes a first step of preparing the substrate 1, a second step of forming the gate electrode 2 on the substrate 1, and a gate as a first insulating film on the gate electrode 2. A third step of forming the insulating film 3, a fourth step of forming a semiconductor thin film to be the channel layer 4 on the gate insulating film 3, and a second step of forming the channel protective film 5 as the second insulating film on the channel layer 4. 5th step, a sixth step of increasing the transmittance of the channel protective film 5 by irradiating the channel protective film 5 with laser light, and a seventh step of forming the source electrode 7S and the drain electrode 7D above the channel layer 4 And a process.

  Hereafter, each process in the manufacturing method of the thin film semiconductor device which concerns on this Embodiment is demonstrated in detail using drawing.

First, as shown in FIG. 2A, a glass substrate is prepared as the substrate 1. Before forming the gate electrode 2, an undercoat layer made of a silicon nitride film, a silicon oxide film, a silicon oxynitride film, or the like may be formed on the surface of the substrate 1 by plasma CVD (Chemical Vapor Deposition) or the like. Good. The undercoat layer is preferably a silicon oxide film (SiO _y ) of 1.5 <y <2.0, and has a thickness of 300 nm to 1500 nm. A more preferable thickness range of the undercoat layer is 500 nm or more and 1000 nm or less. This is because if the thickness of the undercoat layer is increased, the thermal load on the substrate 1 can be reduced, but if it is too thick, film peeling and cracks occur. The step of preparing the substrate 1 includes a step of cleaning the substrate 1 in addition to the step of forming the undercoat layer.

Next, as shown in FIG. 2B, a gate electrode 2 having a predetermined shape is formed on the substrate 1. For example, a gate metal film made of a refractory metal containing Mo or MoW or an alloy of the refractory metal is formed on the substrate 1 by sputtering as the gate electrode 2, and the gate metal film is formed using a photolithography method and a wet etching method. The gate electrode 2 having a predetermined shape can be formed by patterning. MoW wet etching can be performed using, for example, a chemical solution in which phosphoric acid (HPO ₄ ), nitric acid (HNO ₃ ), acetic acid (CH ₃ COOH), and water are mixed in a predetermined composition. When an undercoat layer is formed on the surface of the substrate 1, the gate electrode 2 is formed on the undercoat layer.

  Next, as shown in FIG. 2C, a gate insulating film 3 is formed on the substrate 1 and the gate electrode 2 so as to cover the gate electrode 2. For example, a silicon oxide film, a silicon nitride film, or a laminated film thereof is formed on the gate electrode 2 as the gate insulating film 3 by plasma CVD.

Next, as shown in FIG. 2D, an amorphous semiconductor thin film 4 a that becomes the channel layer 4 is formed on the gate insulating film 3. For example, an amorphous silicon thin film made of amorphous silicon is formed on the gate insulating film 3 by plasma CVD or the like as the amorphous semiconductor thin film 4a. This amorphous silicon thin film can be formed, for example, by introducing silane gas (SiH ₄ ) and hydrogen gas (H ₂ ) at a predetermined concentration ratio. Note that the amorphous silicon thin film can be formed continuously with the gate insulating film 3 by plasma CVD.

  Next, as shown in FIG. 2E, an organic film 5a made of an organic material is formed as a precursor of the channel protective film 5 on the amorphous semiconductor thin film 4a by a predetermined coating method. For example, the organic film 5a is formed on the entire surface of the amorphous semiconductor thin film 4a by applying and spin-coating a predetermined organic material onto the amorphous semiconductor thin film 4a. As the predetermined organic material of the organic film 5a, the above-described photosensitive coating type organic material containing silicon, oxygen, and carbon can be used. Moreover, it is preferable that the organic film 5a is formed so that the transmittance | permeability with respect to the laser beam irradiated at the next process may be less than 37%. After that, pre-baking is performed on the organic film 5a, and the organic film 5a is temporarily fired. For example, heating is performed at a temperature of about 110 ° C. for about 60 seconds. Thereby, the solvent contained in the organic film 5a is vaporized.

  Next, as shown in FIG. 2F, the organic film 5a is patterned into a predetermined shape by exposure and development using a photomask. As the developer, for example, a 2.38% aqueous solution of TMAH (Tetra Methyl Ammonium Hydroxide) can be used. Thereafter, the organic film 5a is subjected to main baking by performing post baking on the patterned organic film 5a. For example, heating is performed at a temperature of 280 ° C. to 300 ° C. for about 1 hour. Thereby, a part of the organic component in the organic film 5a is vaporized and decomposed to improve the film quality.

  Next, as shown in FIG. 2G, an amorphous semiconductor thin film exposed by scanning a predetermined laser beam relative to the substrate 1 in a certain direction from above the organic film 5a. 4a and the organic film 5a are irradiated with laser light.

  At this time, the organic film 5a irradiated with the laser light has a high transmittance and becomes transparent. In this case, it is preferable to perform the laser light under such conditions that the transmittance of the organic film 5a after the laser light irradiation is 37% or more. The transparency of the organic film 5a occurs when laser light is absorbed by the organic film 5a and a photoreaction or a thermal reaction occurs.

  Further, in the present embodiment, the organic film 5a is transparent, so that the laser light is transmitted through the organic film 5a. As a result, the region of the amorphous semiconductor thin film 4a on which the organic film 5a is formed is also irradiated with laser light. Therefore, since the laser beam is irradiated not only on the region where the organic film 5a is not formed but also on the region where the organic film 5a is formed, the entire amorphous semiconductor thin film 4a irradiated with the laser beam is crystallized. It becomes possible to do. That is, the amorphous semiconductor thin film 4a located below the organic film 5a is also crystallized. By this step, the amorphous semiconductor thin film 4a is crystallized to form the channel layer 4 including a polycrystalline (including microcrystalline) crystallized region. Thus, by irradiating laser light from above the organic film 5a, the amorphous semiconductor thin film 4a is crystallized to form a crystallized region.

  Crystallization of the amorphous semiconductor thin film 4a is manifested when the amorphous semiconductor thin film 4a absorbs laser light energy and rises in temperature. In the present embodiment, since an amorphous silicon film is used as the amorphous semiconductor thin film 4a, not only the case where amorphous silicon rises to a temperature of 1414 ° C. (melting point of silicon) or more and becomes polycrystalline, The case where the amorphous silicon is microcrystallized through a solid phase growth or a supercooled liquid state at a temperature of about 750 to 1414 degrees is also included. In this case, the average crystal grain size of crystalline silicon in the channel layer 4 is about 5 nm to 1000 nm. The channel layer 4 includes not only polycrystalline silicon having an average crystal grain size of 100 nm or more, but also an average crystal grain size of 5 nm. In some cases, microcrystalline silicon called microcrystal (μc) of ˜100 nm is also included.

  As described above, in the present embodiment, the substrate 1 is irradiated with laser light by relatively scanning the laser light, thereby making the organic film 5a transparent and the amorphous semiconductor thin film 4a crystallized. Are performed simultaneously.

  Further, in the present embodiment, the organic film 5a is inorganicized by irradiating the organic film 5a with laser light. The inorganicization of the organic film 5a is caused by the thermal reaction by the organic film 5a itself due to the absorption of the laser light by the organic film 5a, and the amorphous semiconductor thin film 4a when the amorphous semiconductor thin film 4a is crystallized. Caused by the heat of formation. At this time, the temperature of the organic film 5a is preferably 600 degrees or more. The details of mineralization of the organic film 5a will be described later.

  The laser light in this step is determined in consideration of the inorganicization of the organic film 5a and the crystallization of the amorphous semiconductor thin film 4a, as will be described later. For example, as the laser light source of the laser light, a light source that emits light having a wavelength in the ultraviolet region, visible light region, or infrared region can be used. These light sources are transparent organic films shown in FIG. Depending on the process of crystallization and the process of crystallization of the semiconductor thin film, they can be used properly. In this embodiment mode, a laser that emits light having a wavelength in the ultraviolet region can be used. For example, an excimer laser whose emission wavelength at which the absorption coefficient of the organic film changes sharply from an opaque region to a transparent region is about 190 nm to 350 nm can be used.

  In addition, although the amorphous semiconductor thin film 4a and the organic film 5a are irradiated with the laser beam condensed linearly, there are, for example, two methods of irradiation. One is a method of moving the stage on which the substrate 1 on which the amorphous semiconductor thin film 4a and the organic film 5a are formed is moved by fixing the irradiation position of the laser beam condensed linearly. The other is a method of fixing the stage (substrate 1) and moving the irradiation position of the laser beam. In either method, the laser beam is irradiated while moving relative to the amorphous semiconductor thin film 4a and the organic film 5a.

  Next, as shown in FIG. 2H, the contact layer 6 is formed so as to extend from the upper surface of the channel protective film 5 to the upper surface of the channel layer 4. Specifically, a contact layer made of amorphous silicon doped with an impurity of a pentavalent element such as phosphorus by plasma CVD so as to cover the upper surface and side surfaces of the channel protective film 5 and the upper surface of the channel layer 4. 6 is formed.

  Next, as shown in FIG. 2I, the source / drain metal film 7 to be the source electrode 7S and the drain electrode 7D is formed so as to cover the contact layer 6. For example, the source / drain metal film 7 having a three-layer structure of MoW / Al / MoW is formed by sputtering.

  Thereafter, although not shown, in order to pattern the source electrode 7S and the drain electrode 7D having a predetermined shape, a resist material is applied onto the source / drain metal film 7, exposed and developed, and patterned into a predetermined shape. Form.

  Next, etching is performed using this resist as a mask to pattern the source / drain metal film 7, thereby forming a source electrode 7S and a drain electrode 7D having a predetermined shape as shown in FIG. At this time, the contact layer 6 functions as an etching stopper. Thereafter, the resist on the source electrode 7S and the drain electrode 7D is removed, and dry etching is performed using the source electrode 7S and the drain electrode 7D as a mask, thereby patterning the contact layer 6 and patterning the channel layer 4 in an island shape. Thereby, a pair of contact layers 6 having a predetermined shape and an island-shaped channel layer 4 can be formed. As dry etching conditions, for example, a chlorine-based gas can be used.

  As described above, the thin film semiconductor device 10 according to the present embodiment can be manufactured.

  Next, the characteristics of the thin film semiconductor device according to the present embodiment will be described with reference to FIGS. 3A to 14 including the background to the invention.

  First, the problem of the conventional thin film semiconductor device 100 will be described with reference to FIGS. 3A, 3B, and 4. FIG. 3A and 3B are cross-sectional views showing the configuration of a conventional thin film semiconductor device. FIG. 4 is a diagram showing current-voltage characteristics of a conventional thin film semiconductor device.

  The conventional thin film semiconductor device 100 shown in FIGS. 3A and 3B and the thin film semiconductor device 10 according to the present embodiment shown in FIG. 1 are different in the configuration of the channel protective film, and the channel protection of the conventional thin film semiconductor device 100 is different. Although the film 105 is made of an organic material, it is not irradiated with a laser and is not made transparent or inorganic.

  In the conventional thin film semiconductor device 100 having such a configuration, as shown in FIG. 3A, the channel protective film 105 made of an organic material contains a lot of positive fixed charges. For this reason, a weak voltage (Vf) is applied to the channel layer 4 (near the interface between the channel protective film 5 and the channel layer 4) under the channel protective film 105 by the fixed charge. In this case, when the voltage (Vf) due to the fixed charge becomes equal to or higher than the back channel threshold voltage (Vbc) in the channel layer 4, the parasitic transistor operates to form a back channel. As a result, the leakage current increases, and the off characteristics of the thin film semiconductor device deteriorate as shown in FIG.

  Further, the channel protective film 105 has a large number of trap levels due to impurities contained in the channel protective film 105 made of an organic material, and carriers are easily trapped by the trap levels. Since carriers are trapped by this trap level, as shown in FIG. 4, the threshold voltage of the thin film semiconductor device 100 is shifted, the reliability of the thin film semiconductor device is deteriorated, and the electrical characteristics vary, resulting in variations in the substrate surface. The internal uniformity may deteriorate.

  As described above, a thin film semiconductor device having a channel protective film of an organic material has a problem that off characteristics and reliability are poor.

  Therefore, the inventors of the present application conducted the following experiments and made extensive studies. As a result, the channel protective film made of an organic film is made inorganic, that is, the stoichiometry of the organic film is made closer to the stoichiometry of the inorganic film. It has been found that the above problems can be solved by modifying the membrane. Details will be described below.

  First, an inorganic film made of an inorganic material is a silicon oxide film. Therefore, first, in order to investigate the chemical structure of the silicon oxide film, a silicon oxide film of about 100 nm was formed on the silicon substrate, and the IR spectrum was measured. FIG. 5 is a diagram showing an IR spectrum of the silicon oxide film.

As a result of the measurement, as shown in FIG. 5, it was found that the silicon oxide film has three peaks as Si—O—Si vibration. Specifically, Si—O—Si (rolling vibration) at 480 cm ⁻¹ (A), Si—O—Si (bending vibration) at 780 cm ⁻¹ (B), and 1080 cm ⁻¹ (C). Si-O-Si (stretching vibration) can be confirmed.

  Next, in order to investigate the chemical structure of the organic film, an organic film made of an organic material of about 100 nm was formed on a silicon substrate, and an IR spectrum was measured. Moreover, although the organic film was solidified by heat treatment, the temperature dependence of the IR spectrum of the organic film was also examined. FIG. 6 is a diagram showing an IR spectrum of the organic film. In addition, the organic material used the organic material of the channel protective film 5 in this Embodiment mentioned above. The organic film was baked for 20 minutes.

As a result of the measurement, as shown in FIG. 6, it was found that nine peaks A to I were observed in the organic film. Specifically, Si—O—Si (rolling) at 480 cm ⁻¹ (A), C—H (variable angle (aromatic)) at 700 cm ⁻¹ (B), and 780 cm ⁻¹ (C). Si—O—Si (variable angle), Si—O—Si (stretching) at 1080 cm ⁻¹ (D), Si-phenyl at 1130 cm ⁻¹ (E), and Si—CH at 1280 cm ⁻¹ (F) ₃ (inclination), Si-phenyl at 1430 cm ⁻¹ (G), CC (stretching (aromatic)) at 1500 cm ⁻¹ (H), and CC (stretching) at 1580 cm ⁻¹ (I) (Aromatic)).

  Further, although the bake temperature is measured by changing in the temperature range of 300 to 600 degrees, as shown in FIG. 6, as the bake temperature rises, Si—O—Si bonds increase and Si—OH increases. It can be confirmed that the Si-phenyl bond is reduced.

  Based on the results shown in FIG. 5 and FIG. 6, the inventor of the present application can obtain the knowledge that the stoichiometry of the organic film can be brought close to the stoichiometry of the inorganic film by heating the organic film. It was.

  However, as shown in FIG. 6, it can be seen that a considerable amount of organic components remain even after heat treatment at 600 degrees. Therefore, it is considered that the organic film can be made more inorganic by performing a heat treatment of 600 ° C. or more on the organic film. However, if the baking temperature is set to 600 ° C. or higher, the glass substrate is melted. It is difficult to make the temperature 600 degrees or more. Further, when the baking temperature is set to 600 ° C. or higher, the thin film transistor cannot be manufactured using a low temperature process whose upper limit is about 400 ° C. Usually, the baking temperature of the channel protective film of the organic film is about 400 ° C. at the maximum, so it is not preferable to set the baking temperature to 600 ° C. or higher. As described above, since the entire substrate is exposed to a high temperature, baking has a limit in raising the baking temperature.

  Therefore, the inventor of the present application has considered that the organic film is heated to 600 ° C. or higher by irradiating the organic film with laser light. In the case of laser light, the irradiated portion of the laser light can be locally heated to a high temperature, so that the thin film transistor can be manufactured without melting the glass substrate and using a low temperature process.

  FIG. 7 is a diagram showing the IR spectrum of the organic film, and shows the result of IR measurement after the organic film was heat-treated for 5 minutes in the temperature range of 300 to 1100 degrees. Note that the organic film in FIG. 7 is composed of an organic material (material A) containing siloxane in the main skeleton.

7, with an increase in temperature, vibration mode disappears due to organic substances such as Si-CH ₃ peak is observed (deformation) in 1280 cm ^-1, a peak is observed at 1080 cm ^-1 It can be seen that Si—O—Si (stretching) increases and SiO bonding increases. In particular, it can be seen that the spectrum suddenly changes between 500 degrees and 600 degrees. (A) of FIG. 8A and (a) of FIG. 8B are enlarged views of (c) and (d) of FIG. 7, respectively. FIG. 8A (b) and FIG. 8B (b) are enlarged views of regions surrounded by broken lines in FIG. 8A (a) and FIG. 8A (a), respectively.

As shown in FIGS. 8A and 8B, it can also be seen that the absorption coefficient suddenly increases and the half-value width suddenly decreases between 500 degrees and 600 degrees. Thus, in this embodiment, the half width of the peaks present in 1080 cm ^-1 in the 500 ° and 600 ° IR spectrum of the organic film varies suddenly ^{(60cm -1 + 170cm -1) /} 2 = 115cm -1 The following cases are defined as mineralization.

  Next, optical characteristics of the organic film formed of the organic material (material A) with respect to laser light will be described with reference to FIGS. 9A, 9B, 10A, and 10B. 9A and 9B show the wavelength dependency of the refractive index of the organic film and the dependency of the heat treatment temperature when the organic film of the material A is heat-treated. The wavelength of the irradiated laser light, the organic film It is the figure which showed the relationship between the heat processing temperature of and the refractive index of an organic film. 10A and 10B show the wavelength dependency of the extinction coefficient of the organic film and the dependency of the heat treatment temperature when the organic film of the material A is heat-treated. FIG. 5 is a graph showing the relationship between the heat treatment temperature of the organic film and the extinction coefficient of the organic film. FIG. 9B shows the same characteristics as FIG. 9A, except that the parameters on the horizontal axis are different from those in FIG. 9A. FIG. 10B also shows the same characteristics as FIG. 10A.

  First, as shown in FIGS. 9A and 9B, it can be seen that as the heating temperature of the organic film increases, the refractive index decreases and approaches the refractive index of silicon oxide (n = 1.4). That is, it can be seen from the viewpoint of refractive index that the organic film can be brought closer to the silicon oxide film by heating the organic film with laser light.

Further, as shown in FIGS. 10A and 10B, it can be seen that the extinction coefficient decreases as the heating temperature of the organic film increases. That is, the organic film can be made transparent by heating the organic film with laser light. In FIGS. 10A and 10B, data is not plotted for a temperature range from about 800 degrees to about 900 degrees, because this exceeds the detection limit of the measuring apparatus. In this range, the extinction coefficient is small and is not more than 1 × 10 ⁻⁷ cm ⁻¹ . A spectroscopic ellipsometer was used as the measuring device.

  The absorption coefficient α can be expressed as α = 4πk / λ where λ is the incident wavelength and k is the extinction coefficient. Therefore, the extinction coefficient characteristic shown in FIGS. 10A and 10B is the characteristic of the absorption coefficient. As shown in FIGS. 11A and 11B. FIG. 11A and FIG. 11B show the wavelength dependency of the absorption coefficient of the organic film and the dependency of the heat treatment temperature when the organic film of the material A is heat-treated. It is a figure which shows the relationship between the heat processing temperature of and the absorption coefficient of an organic film. Note that FIG. 11B shows the same characteristics as FIG. 11A except that the parameters on the horizontal axis are different from those in FIG. 11A.

As shown in FIGS. 11A and 11B, the absorption coefficient of the organic film (material A) is constant or slightly increased up to 500 degrees, but it can be seen that it decreases by an order of magnitude or more from 500 degrees to 600 degrees. Moreover, it turns out that an absorption coefficient becomes still smaller when it exceeds 600 degree | times and becomes still higher temperature. In FIGS. 11A and 11B, data is not plotted for a temperature range from about 800 ° C. to about 900 ° C., but as in FIG. The coefficient is 1 × 10 ⁻¹ cm ⁻¹ or less.

  As described above, it can be understood that the temperature of the organic film is increased by the irradiation of the laser beam, and thereby the absorption coefficient is reduced and the organic film becomes transparent. Further, it can be seen that when the temperature of the organic film rises, the vibration mode caused by the organic matter disappears and the bonding of SiO increases, thereby making it inorganic.

  Next, the result of measuring the wavelength and temperature dependence of the absorption coefficient in the organic film in the same manner as in FIGS. 11A and 11B by changing the material of the organic film will be described. 12A and 12B show the wavelength dependency of the absorption coefficient of the organic film and the dependency of the heat treatment temperature when the organic film formed of the material B is heat treated. 13A and 13B show the wavelength dependency of the absorption coefficient of the organic film and the dependency of the heat treatment temperature when the organic film formed of the material C is heat treated. Note that FIGS. 12B and 13B show the same characteristics as FIGS. 12A and 12B, respectively, except that the parameters on the horizontal axis differ from FIGS. 12A and 13A.

  Here, like the material A, the material B is an organic material containing siloxane in the main skeleton. Material C is an organic material containing silsesquioxane in the main skeleton. The other configurations of the material B and the material C are the same as the material A.

  As shown in FIGS. 12A and 12B, the absorption coefficient of the organic film (material B) is constant or slightly increased up to 500 degrees as in the case of the organic film (material A), but when it becomes 500 degrees to 600 degrees. It can be seen that it is one digit smaller. Moreover, it turns out that an absorption coefficient becomes still smaller when it exceeds 600 degree | times and becomes still higher temperature.

As shown in FIGS. 13A and 13B, the absorption coefficient of the organic film (material C) is constant or slightly increased up to 500 degrees as in the organic film (material A), but is 500 degrees to 600 degrees. It turns out that becomes smaller by one digit or more. Moreover, it turns out that an absorption coefficient becomes still smaller when it exceeds 600 degree | times and becomes still higher temperature. In FIG. 13A and FIG. 13B, data is not plotted for a temperature range from about 700 degrees to about 900 degrees. However, as in FIG. The coefficient is 1 × 10 ⁻¹ cm ⁻¹ or less.

  As described above, it can be seen that even an organic film made of a different organic material increases in temperature due to laser light irradiation, thereby reducing the absorption coefficient and making it transparent. Further, it can be seen that when the temperature of the organic film rises, the vibration mode caused by the organic matter disappears and the bonding of SiO increases, thereby making it inorganic.

  It can also be seen that the absorption coefficient with respect to the wavelength of the laser beam can be changed by changing the material of the organic film. This makes it possible to select the type of organic material and the wavelength of the laser light so that it is non-transparent (colored) before laser light irradiation and transparent after laser light irradiation. .

  In the present embodiment, the non-transparent organic film 5a that is the precursor of the channel protective film 5 is irradiated with laser light to make the organic film 5a transparent to form the channel protective film 5, and at the same time The amorphous semiconductor thin film 4a under the channel protective film 5 is crystallized. Therefore, the material of the organic film 5a and the wavelength of the laser light are selected so that the transmittance before laser light irradiation is less than 37% and the transmittance after laser light irradiation is 37% or more. Is preferred.

Here, the transmittance τ of the organic film is represented by τ = I / I ₀ when expressed using the intensity I _{0 of the} incident light and the intensity I of the light that has passed through the organic film. the absorption coefficient alpha, expressed by using the thickness t of the organic layer, can be expressed by _{τ = I / I 0 = exp} (-αt). In this embodiment, if the organic film is opaque, and the product of the absorption coefficient α of the organic film and the film thickness t of the organic film is greater than 1, in this case, the transmission is −αt = −1. Since the rate τ is τ = exp (−1) = 0.36789≈37%, the transmittance is less than 37%. On the other hand, when the product of the organic film is transparent and the product of the absorption coefficient α of the organic film and the film thickness t of the organic film is 1 or less, in this case, the transmittance is 37% or more. The absorptance can be expressed by 1-transmittance (τ).

FIG. 14 is a diagram showing the relationship of the transmittance of the organic film to the absorption coefficient α (cm ⁻¹ ) of the organic film and the film thickness t (cm) of the organic film. As shown in FIG. 14, in the present embodiment, the case where the transmittance of the organic film is less than 37% is opaque, and the case where the transmittance of the organic film is 37% or more is transparent.

  Thus, by using FIG. 14 and FIGS. 11A to 13B, a desired organic material type, laser that is opaque before being irradiated with laser light and transparent after being irradiated with laser light. The wavelength of light and laser irradiation conditions (heating temperature) can be selected.

  As described above, according to the thin film semiconductor device 10 according to the present embodiment, the organic film 5a formed on the amorphous semiconductor thin film 4a is irradiated with a desired laser beam, thereby transmitting the organic film 5a. The organic film 5a can be made transparent by increasing the rate, and the temperature of the organic film 5a can be increased to make the organic film 5a inorganic. In the present embodiment, the laser light is transmitted along with the transparency of the organic film 5a, whereby the amorphous semiconductor thin film 4a under the organic film 5a is crystallized. In this case, the heat at the time of crystallization of the amorphous semiconductor thin film 4a is conducted to the organic film 5a, and the temperature of the organic film 5a is increased by this heat and the organic film 5a becomes inorganic. That is, in the present embodiment, the organic film 5a is mineralized by heat generated by the organic film 5a itself by absorbing laser light and heat generated during crystallization of the amorphous semiconductor thin film 4a. In this way, in the present embodiment, the channel protective film 5 that has been made transparent and inorganic can be formed.

  Therefore, as shown in FIG. 15A, since the channel protection film 5 is mineralized, the fixed charge of the channel protection film 5 is reduced, so that the formation of the back channel can be suppressed. Thereby, a thin film semiconductor device having excellent off characteristics can be realized.

  Further, by making the channel protective film 5 inorganic, as shown in FIG. 15B, the trap level of the channel protective film 5 can also be reduced, so that trapping of carriers in the channel protective film 5 can be suppressed. . Thereby, since the shift of the threshold voltage in the thin film semiconductor device can be suppressed, a thin film semiconductor device having excellent reliability and high in-plane uniformity can be realized.

  In the present embodiment, the thickness of the channel protective film 5 is preferably in the range described below.

  FIG. 16 is a diagram showing a change in the absorptance of the amorphous semiconductor thin film 4a when the thickness of the channel protective film 5 is changed. In FIG. 16, the horizontal axis represents the value obtained by dividing the optical film thickness of the channel protective film 5 by the wavelength of the laser beam, and the vertical axis represents the absorptance of the amorphous semiconductor thin film 4a. In the calculation of FIG. 16, the gate insulating film 3 is made of silicon oxide, and the optical film thickness of the gate insulating layer 3, that is, the value obtained by adding the refractive index of the gate insulating layer 3 to the film thickness of the gate insulating layer 3 The value divided by the wavelength of light is 0.276 (corresponding to a wavelength of 532 nm and a silicon oxide layer thickness of 100 nm), and the amorphous semiconductor thin film 4a (amorphous silicon thin film) under the channel protective film 5 From the value obtained by integrating the refractive index of the amorphous semiconductor thin film 4a to the optical film thickness divided by the wavelength of the laser beam is 0.477 (corresponding to the film thickness of the amorphous silicon layer at a wavelength of 532 nm and 50 nm). Therefore, a model is used in which the channel protective layer 5 is made of silicon oxide. And the broken line of FIG. 16, the dashed-two dotted line, and the continuous line have shown the calculation result in case the gate electrode 2 is Cu, Al, and MoW, respectively.

  As shown in FIG. 16, when the value obtained by dividing the optical film thickness of the channel protective film 5 by the wavelength of the laser beam is Z, k is an integer starting from 0, and if Z satisfies the following (Equation 1), it is amorphous. The absorption efficiency of the laser beam in the high-quality semiconductor thin film 4a can be increased. Note that k = 0, 1, and 2 in FIG. 16 indicate the range of Z when k = 0, 1, and 2 in (Equation 1), respectively.

  (Formula 1) 0.5 × (k + 0.3) ≦ Z ≦ 0.5 × (k + 0.7)

  Thus, by setting the film thickness of the channel protective film 5 so as to satisfy the condition of (Equation 1), the absorption efficiency of laser light in the amorphous semiconductor thin film 4a under the channel protective film 5 is increased. Therefore, the region under the channel protective film 5 can be efficiently heat-treated, the amorphous semiconductor thin film can be efficiently crystallized, and the channel protective film 5 can be thermally propagated from the semiconductor thin film. Can be made transparent efficiently. Thereby, a thin film semiconductor device having excellent off characteristics and reliability can be realized.

  In the present embodiment, the organic film 5a is pre-baked in FIG. 2E. At this time, the interface layer 50 is formed at the interface between the amorphous semiconductor thin film 4a and the organic film 5a. May generate. The interface layer 50 contains carbon as a main component, and the main component carbon is carbon derived from the organic material of the organic film 5a.

  FIG. 17A is a cross-sectional view showing the configuration of the thin film semiconductor device 10A according to the first embodiment when the interface layer 50 is formed.

As shown in FIG. 17A, the interface layer 50 is formed between the channel layer 4 and the channel protective film 5. The interface layer 50 is an insulating film having an insulating property, and the specific resistance of the interface layer 50 is preferably 2 × 10 ⁶ (Ω · cm) or more.

As shown in FIG. 17A, in the thin film semiconductor device 10A, a pair of amorphous silicon thin films 60 are formed between the interface layer 50 and the contact layer 6. The amorphous silicon thin film 60 is an i layer made of an amorphous silicon film and not intentionally doped with impurities. Therefore, the amorphous silicon thin film 60 has a higher electrical resistance than the contact layer 6 doped with impurities. However, the amorphous silicon thin film 60 contains naturally contained impurities, and the impurity concentration of the amorphous silicon thin film 60 is 1 × 10 ¹⁷ (atm / cm ³ ) or less.

  Next, the configuration of the interface layer 50 in the thin film semiconductor device 10A illustrated in FIG. 17A will be described with reference to FIGS. 18A and 18B. 18A is a cross-sectional TEM image around the interface layer of the thin film semiconductor device shown in FIG. 17A. FIG. 18B is a schematic diagram for explaining a cross-sectional structure of a region B surrounded by a broken line in FIG. 18A.

  As shown in FIG. 18A, it can be seen that an ultrathin interface layer 50 is formed at the interface between the channel layer 4 and the channel protective film 5. Further, FIG. 18A shows that the interface layer 50 having a thickness of about 2 nm is formed.

  As described above, the interface layer 50 is a layer generated when the channel protective film 5 is heated and solidified, and the channel layer 4 side of the interface layer 50 is a precursor of the channel protective film 5 as shown in FIG. 18B. It is considered that the silicon compound of the surfactant contained in the material of the organic film 5a that is the body and the silicon atoms of the channel layer 4 are bonded.

Specifically, as shown in FIG. 18B, at the interface between the interface layer 50 and the channel layer, the surfactant Y—Si— (O) ₃ and the crystalline silicon thin film Si are bonded to each other, and the Si—O— Si bonds are present. Y in Y—Si— (O) ₃ is a functional group that reacts with an organic material and is an amino group, an epoxy group, a methacryl group, a vinyl group, a mercapto group, or the like.

  In addition, the channel protective film 5 side of the interface layer 50 is composed of a SiOC-based polymer (a thin film formed with at least Si, O, and C as main components) and an S (sulfur) -based polymer (constituting elements such as Si, O, C, The thin film containing S) is present. The SiOC-based polymer is considered to be a polymer of the surfactant silicon compound contained in the material of the organic film 5a and the carbon contained in the photosensitive organic resin material. The S-based polymer is considered to be a thin film obtained by polymerizing a photosensitive agent, a surfactant and a photosensitive agent contained in the organic material of the organic film 5a.

  Thus, the interface layer 50 is considered to have a configuration in which the Si—O—Si bonds and the polymer are combined into a matrix. On the interface layer 50, there is a channel protective film 5 made of a bulk SiOC-based polymer.

  It is apparent from FIG. 18A that the interface layer 50 is made of a material different from both the channel layer 4 and the channel protective film 5. That is, as shown in the TEM image of FIG. 18A, layers having different contrasts can be confirmed between the channel layer 4 and the channel protective film 5. Note that the difference in contrast in the TEM image indicates that the density of the material is different, which means that different layers exist. Therefore, the interface layer 50 exists between the channel layer 4 and the channel protective film 5 as a layer different from these layers.

  Next, the concentration distribution of carbon (C) and sulfur (S) in the thin film semiconductor device 10A shown in FIG. 17A will be described with reference to FIG. FIG. 19 is a view showing the concentration distribution of carbon and sulfur contained in the film constituting the thin film semiconductor device shown in FIG. 17A, and shows the element concentration in the thickness (depth) direction indicated by arrow A in FIG. 17A. It is measured and plotted by secondary ion mass spectrometry (SIMS).

  In the thin film semiconductor device 10A shown in FIG. 17A, when the carbon and sulfur concentrations are measured according to the depth direction of the arrow A in FIG. 17A, that is, the contact layer 6, the amorphous silicon thin film 60, the interface layer 50, and the channel layer. When the carbon and sulfur concentrations are measured in the order of 4, the measurement results shown in FIG. 19 are obtained. In FIG. 19, the curves indicated by “12C” and “32S” represent the concentration distributions of carbon and sulfur, respectively.

As shown in FIG. 19, the interface layer 50 has a higher carbon concentration and sulfur concentration than the other layers, and the carbon concentration contained in the interface layer 50 is 5 × 10 ²⁰ (atoms / cm ³ ) or more. In addition, it can be seen that the concentration of sulfur contained in the interface layer 50 is 5 × 10 ¹⁹ (atoms / cm ³ ) or more.

  Further, it can be seen that the carbon concentration contained in the interface layer 50 is 50 times or more the carbon concentration as an impurity contained in the channel layer 4. It can also be seen that the sulfur concentration contained in the interface layer 50 is 100 times or more the sulfur concentration as an impurity contained in the channel layer 4.

  The interface layer 50 formed in this manner contains carbon as a main component, and therefore contains more carbon than the channel layer 4. As described above, since the interface layer 50 containing carbon as a main component exists at the interface between the convex portion of the channel layer 4 and the channel protective layer 5, the scattering is increased at the interface between the channel protective layer 5 and the channel layer 4. The interface layer 50 functions as a barrier that blocks carrier movement. That is, the resistance value in the upper part of the channel layer 4 can be increased. Thereby, the carrier mobility in the back channel region of the channel layer 4 can be reduced.

  The sulfur contained in the interface layer 50 is sulfur contained in the organic material photosensitizer of the channel protective layer 5. That is, the sulfur contained in the interface layer 50 is derived from the organic material of the channel protective layer 5. Since sulfur has a larger atomic radius than carbon and oxygen, the effect of preventing carrier movement is larger than that of carbon and oxygen. Therefore, when the interface layer 6 contains sulfur, the carrier mobility can be further reduced, and the off characteristics of the thin film semiconductor device can be further improved.

  Thereby, even if a fixed charge is generated in the channel protective layer 5, back channel conduction of carriers can be suppressed by scattering by the interface layer 50.

  In the thin film semiconductor device 10A shown in FIG. 17A, the interface layer 50 is intentionally left on the entire surface of the channel layer 4 without removing the interface layer 50 in order to examine the components of the interface layer 50 in detail. However, from the viewpoint of improving the TFT characteristics, it is preferable to sufficiently remove the interface layer 50 existing in the current path. That is, in the thin film semiconductor device 10A shown in FIG. 17A, since the high resistance interface layer 50 exists between the contact layer 60 and the channel layer 4 serving as a current path, the on-characteristics are deteriorated. Therefore, in order to realize a thin film semiconductor device having excellent on-characteristics, when the organic film 5a is patterned into a predetermined shape, the interface layer 50 that can remain as a residue is sufficiently removed using development processing or etching processing. Accordingly, it is preferable that the high-resistance interface layer 50 does not exist between the contact layer 60 serving as a current path and the channel layer 4 as in the thin film semiconductor device 10B illustrated in FIG. 17B.

  As described above, according to the other thin film semiconductor device 10B according to the first embodiment of the present invention, the interface layer 50 containing carbon as a main component between the upper portion of the channel layer 4 and the channel protective layer 5 is provided. Since it is formed, the carrier mobility in the back channel region of the channel layer 4 can be reduced. Thereby, the leakage current at the time of OFF can be suppressed, so that the OFF characteristics can be improved.

(Second Embodiment)
Next, a method for manufacturing a thin film semiconductor device according to the second embodiment of the present invention will be described with reference to FIG. FIG. 20 is a cross-sectional view for explaining the method for manufacturing the thin film semiconductor device according to the second embodiment of the present invention. In FIG. 20, the same components as those shown in FIG.

  The configuration of the thin film semiconductor device manufactured by the manufacturing method according to the present embodiment is the same as the configuration of the thin film semiconductor device 10 according to the first embodiment. That is, the present embodiment is different from the first embodiment in the manufacturing method.

  Specifically, in the manufacturing method in the first embodiment, as shown in FIG. 2F, the organic film 5a is made transparent by irradiating the organic film 5a once. In this embodiment, the organic film 5a is made transparent and mineralized, and the amorphous semiconductor thin film 4a is crystallized. It is done in a separate process.

  Hereinafter, a specific method for manufacturing the thin film semiconductor device according to the present embodiment will be described with reference to FIG.

  First, as shown in FIGS. 20A to 20E, the same steps as in FIGS. 2A to 2E are performed. Thereby, as shown in FIG. 20E, a patterned organic film 5a having a predetermined shape is formed on the amorphous semiconductor thin film 4a.

  Next, as shown in FIG. 20G, the organic film 5a is irradiated with laser light in order to make the organic film 5a transparent and inorganic. As a result, the organic film 5a absorbs the energy of the laser beam and undergoes a photoreaction or a thermal reaction, and is modified from opaque to transparent to become transparent. At the same time, the organic film 5a absorbs the energy of the laser beam and undergoes a photoreaction or thermal reaction, and the organic film 5a becomes inorganic. Thereby, the channel protective film 5 which is made transparent and inorganic is formed.

  In this case, the degree of transparency and mineralization of the organic film 5a is determined by the temperature of the organic film 5a and the like. Specifically, it is determined according to the temperature and the like shown in FIGS. 9A to 13B.

  Also in this embodiment, the transmittance of the channel protective film 5 with respect to the laser beam is less than 37% before the laser beam irradiation, and is preferably 37% or more after the laser beam irradiation. That is, in this step, the channel protective film 5 is formed under conditions, materials, and the like such that the transmittance for laser light is 37% or more.

  Thus, by setting the transmittance to 37% or more after laser light irradiation, the laser light for crystallization of the amorphous semiconductor thin film 4a can be easily transmitted to the channel protective film 5. . Thereby, since the amorphous semiconductor thin film 4a located below the channel protective film 5 can be easily crystallized, the heat generated when the amorphous semiconductor thin film 4a is crystallized is directly protected by the channel protection. The film 5 can be efficiently conducted. Therefore, in the next step, the inorganicization of the channel protective film 5 can be promoted.

  Next, as shown in FIG. 20H, the amorphous semiconductor thin film 4a is crystallized by annealing the amorphous semiconductor thin film 4a. As a result, a channel layer 4 having a channel region can be formed on the gate insulating film 3 as shown in FIG.

  In the present embodiment, the amorphous semiconductor thin film 4a is crystallized by irradiating the amorphous semiconductor thin film 4a with laser light from above the channel protective film 5, as shown in FIG. At this time, since the channel protective film 5 is made transparent, the laser light passes through the channel protective film 5 and is also irradiated to the amorphous semiconductor thin film 4 a under the channel protective film 5. Therefore, the amorphous semiconductor thin film 4a below the channel protective film 5 can also be crystallized.

  As the laser light source of the laser light, a light source that emits light having a wavelength in the ultraviolet region, visible light region, or infrared region can be used. These light sources are transparent organic films shown in FIG. It can be used properly according to each of the crystallization process or the crystallization process of the semiconductor thin film shown in FIG.

  In this embodiment mode, a laser that emits light having a wavelength in the ultraviolet region can be used. Preferably, an excimer laser whose emission wavelength at which the absorption coefficient of the organic film changes abruptly from an opaque region to a transparent region is about 190 nm to 350 nm can be used.

  At this time, the channel protective film 5 is further inorganicized by the heat conducted from the amorphous semiconductor thin film 4 a to the channel protective film 5. For example, if the temperature at the time of laser irradiation when the amorphous semiconductor thin film 4a is crystallized is higher than the temperature at the time of laser irradiation of the organic film 5a, the inorganicization of the channel protective film 5 further proceeds. To do.

  The crystallization of the amorphous semiconductor thin film 4a is not limited to the laser annealing method, and a rapid thermal processing method (RTP) may be used.

  Next, as shown in (i) to (k) of FIG. 20, the same processes as in (h) to (j) of FIG. 2 are performed. Thereby, a thin film semiconductor device having the same configuration as that of the first embodiment can be obtained.

  As described above, according to the method for manufacturing a thin film semiconductor device according to the present embodiment, the transmittance of the organic film 5a is obtained by irradiating the organic film 5a with a desired laser beam, as in the first embodiment. The organic film 5a can be made transparent by increasing the temperature, and the temperature of the organic film 5a can be increased to make the organic film 5a inorganic.

  Thus, since the fixed charge of the channel protective film 5 can be reduced by making the channel protective film 5 inorganic, the formation of the back channel can be suppressed. Thereby, a thin film semiconductor device having excellent off characteristics can be realized.

  In addition, since the trap level of the channel protective film 5 can be reduced by making the channel protective film 5 inorganic, trapping of carriers in the channel protective film 5 can be suppressed. Thereby, since the shift of the threshold voltage in the thin film semiconductor device can be suppressed, a thin film semiconductor device having excellent reliability and high in-plane uniformity can be realized.

  Further, in the present embodiment, the step of increasing the transmittance of the organic film 5a (channel protective film 5) and the step of crystallizing the amorphous semiconductor thin film 4a are performed separately, so that each of the desired conditions Can be irradiated with laser light. Therefore, the transmittance of the organic film 5a can be reliably increased, and the amorphous semiconductor thin film 4a can be reliably crystallized.

(Third embodiment)
Next, a method for manufacturing a thin film semiconductor device according to the third embodiment of the present invention will be described with reference to FIGS. FIG. 21 is a cross-sectional view for explaining the method for manufacturing the thin film semiconductor device according to the third embodiment of the present invention. In FIG. 21, the same components as those shown in FIG.

  The configuration of the thin film semiconductor device manufactured by the manufacturing method according to the present embodiment is the same as the configuration of the thin film semiconductor device 10 according to the first embodiment. That is, the present embodiment is different from the first embodiment in the manufacturing method.

  Specifically, in the manufacturing method in the first embodiment, as shown in FIG. 2 (f), the organic film 5a is irradiated with laser light to make the organic film 5a transparent and inorganic. In this embodiment, as in the second embodiment, the organic film 5a is made transparent and inorganic, and the amorphous semiconductor is crystallized. The thin film 4a is crystallized in separate steps. In the present embodiment, unlike the second embodiment, the amorphous semiconductor thin film 4a is crystallized prior to the transparent and inorganic processes of the organic film 5a.

  Hereinafter, a specific method for manufacturing the thin film semiconductor device according to the present embodiment will be described with reference to FIG.

  First, as shown in FIGS. 21A to 21C, the same steps as in FIGS. 2A to 2C are performed. Thereby, the gate electrode 2 and the gate insulating film 3 having a predetermined shape can be formed on the substrate 1.

  Next, as shown in FIG. 21D, a channel layer 4 made of a crystalline silicon thin film is formed on the gate insulating film 3. The channel layer 4 can be formed by forming an amorphous silicon film as described above, and annealing and crystallizing with a laser or the like as described above. Alternatively, a crystalline silicon thin film can be formed by a method such as direct growth by CVD.

  Next, as shown in FIG. 21E, the same process as in FIG. 2E is performed. That is, an organic film 5a made of an organic material is formed on the channel layer 4 as a precursor of the channel protective film 5 by a predetermined coating method. The organic film 5a is preferably formed so that the transmittance for the next irradiated laser beam is less than 37%. After that, pre-baking is performed on the organic film 5a, and the organic film 5a is temporarily fired.

  Next, as shown in FIG. 21F, the same process as in FIG. 2F is performed. That is, the organic film 5a is patterned into a predetermined shape by exposure and development using a photomask.

  Next, as shown in FIG. 21G, the organic film 5a is irradiated with laser light by scanning a predetermined laser light relative to the substrate 1 in a certain direction by laser annealing. As a result, the organic film 5a irradiated with the laser light becomes transparent with high transmittance. In this case, it is preferable that the transmittance of the organic film 5a after the laser light irradiation is 37% or more. Furthermore, when the organic film 5a is irradiated with laser light, the organic film 5a becomes inorganic.

  In addition, about the kind of organic material of the organic film 5a, the wavelength of a laser beam, and laser irradiation conditions (heating temperature), by using FIG. 14 and FIG. 11A-FIG. 13B similarly to 1st Embodiment. Can be determined.

  Next, as shown in (h) to (j) of FIG. 20, the same processes as in (h) to (j) of FIG. 2 are performed. Thereby, a thin film semiconductor device having the same configuration as that of the first embodiment can be obtained.

  As described above, according to the method for manufacturing a thin film semiconductor device according to the present embodiment, the transmittance of the organic film 5a is obtained by irradiating the organic film 5a with a desired laser beam, as in the first embodiment. The organic film 5a can be made transparent by increasing the temperature, and the temperature of the organic film 5a can be increased to make the organic film 5a inorganic.

  Thus, since the fixed charge of the channel protective film 5 can be reduced by making the channel protective film 5 inorganic, the formation of the back channel can be suppressed. Thereby, a thin film semiconductor device having excellent off characteristics can be realized.

  In addition, since the trap level of the channel protective film 5 can be reduced by making the channel protective film 5 inorganic, trapping of carriers in the channel protective film 5 can be suppressed. Thereby, since the shift of the threshold voltage in the thin film semiconductor device can be suppressed, a thin film semiconductor device having excellent reliability and high in-plane uniformity can be realized.

  Furthermore, in the present embodiment, as in the second embodiment, a step of increasing the transmittance of the organic film 5a (channel protective film 5), a step of crystallizing the amorphous semiconductor thin film 4a, Are performed separately, so that laser light can be irradiated under desired conditions. Therefore, the transmittance of the organic film 5a can be reliably increased, and the amorphous semiconductor thin film 4a can be reliably crystallized.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. This embodiment is an example in which the thin film semiconductor device according to each of the above embodiments is applied to a display device. In this embodiment, an application example to an organic EL display device will be described.

  FIG. 22 is a partially cutaway perspective view of an organic EL display device according to a fourth embodiment of the present invention. The above-described thin film semiconductor device can be used as a switching transistor or a driving transistor of an active matrix substrate in an organic EL display device.

  As shown in FIG. 22, the organic EL display device 20 corresponds to an active matrix substrate (TFT array substrate) 21, a plurality of pixels 22 arranged in a matrix on the active matrix substrate 21, and a plurality of pixels 22. The organic EL element 23 formed in this way, a plurality of scanning lines (gate lines) 27 formed along the row direction of the pixels 22, and a plurality of video signal lines formed along the column direction of the pixels 22 ( Source line) 28 and a power line 29 (not shown) formed in parallel with the video signal line 28. The organic EL element 23 includes an anode 24, an organic EL layer 25, and a cathode 26 that are sequentially stacked on the active matrix substrate 21. Note that a plurality of anodes 24 are actually formed corresponding to the pixels 22. A plurality of organic EL layers 25 are also formed corresponding to the pixels 22, and each layer such as an electron transport layer, a light emitting layer, and a hole transport layer is laminated.

  Next, the circuit configuration of the pixel 22 in the organic EL display device 20 will be described with reference to FIG. FIG. 23 is a diagram showing a circuit configuration of a pixel using the thin film semiconductor device according to the first embodiment of the present invention.

  As shown in FIG. 23, each pixel 22 is partitioned by orthogonal scanning lines 27 and video signal lines 28, and includes a drive transistor 31, a switching transistor 32, a capacitor 33, and an organic EL element 23. . The drive transistor 31 is a transistor that drives the organic EL element 23, and the switching transistor 32 is a transistor for selecting the pixel 22.

  In the drive transistor 31, the gate electrode 31G is connected to the drain electrode 32D of the switching transistor 32, the source electrode 31S is connected to the anode of the organic EL element 23 via a relay electrode (not shown), and the drain electrode 31D is connected to the power line 29. Connected to.

  In the switching transistor 32, the gate electrode 32G is connected to the scanning line 27, the source electrode 32S is connected to the video signal line 28, and the drain electrode 32D is connected to the capacitor 33 and the gate electrode 31G of the driving transistor 31.

  In this configuration, when a gate signal is input to the scanning line 27 and the switching transistor 32 is turned on, the video signal voltage supplied via the video signal line 28 is written to the capacitor 33. The video signal voltage written in the capacitor 33 is held throughout one frame period, and the held video signal voltage changes the conductance of the drive transistor 31 in an analog manner, and the drive current corresponding to the light emission gradation is changed to the organic EL. The organic EL element 23 emits light by flowing from the anode to the cathode of the element 23.

  Note that although an organic EL display device using an organic EL element has been described in this embodiment mode, the present invention can also be applied to other display devices using an active matrix substrate. In addition, the display device configured as described above can be used as a flat panel display and can be applied to an electronic apparatus having any display panel such as a television set, a personal computer, and a mobile phone.

  Although the thin film semiconductor device and the manufacturing method thereof according to the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

  For example, in the above embodiment, the silicon thin film is used as the semiconductor thin film, but a semiconductor thin film other than the silicon thin film can be used. For example, a channel layer made of a crystalline semiconductor thin film can be formed by crystallizing a semiconductor thin film made of germanium (Ge) or SiGe.

  In the above embodiment, the crystalline silicon thin film may be an n-type semiconductor or a p-type semiconductor.

  In addition, it is realized by arbitrarily combining the components and functions in each embodiment without departing from the scope of the present invention, or the form obtained by making various modifications conceived by those skilled in the art to each embodiment. Forms to be made are also included in the present invention.

  The thin film semiconductor device according to the present invention can be widely used for display devices such as a television set, a personal computer, a mobile phone, and other various electric devices having thin film transistors.

DESCRIPTION OF SYMBOLS 1 Substrate 2, 31G, 32G Gate electrode 3 Gate insulating film 4 Channel layer 4a Amorphous semiconductor thin film 5, 105 Channel protective film 5a Organic film 6 Contact layer 7 Source / drain metal film 7D, 31D, 32D Drain electrode 7S, 31S , 32S source electrode 10, 10A, 10B, 100 thin film semiconductor device 20 organic EL display device 21 active matrix substrate 22 pixel 23 organic EL element 24 anode 25 organic EL layer 26 cathode 27 scanning line 28 video signal line 29 power supply line 31 drive transistor 32 switching transistor 33 capacitor 50 interface layer 60 amorphous silicon thin film

Claims (21)

A first step of preparing a substrate;
A second step of forming a gate electrode on the substrate;
A third step of forming a first insulating film on the gate electrode;
A fourth step of forming a semiconductor thin film to be a channel layer on the first insulating film;
A fifth step of forming a second insulating film on the semiconductor thin film;
A sixth step of increasing the transmittance of the second insulating film by irradiating the second insulating film with light;
Forming a source electrode and a drain electrode above the channel layer,
A method for manufacturing a thin film semiconductor device. In the fifth step, the second insulating film made of an organic material having a light transmittance of less than 37% is formed,
In the sixth step, the transmittance of the second insulating film is set to 37% or more by irradiation with the light beam.
A method for manufacturing a thin film semiconductor device according to claim 1. Forming the amorphous semiconductor thin film in the fourth step;
In the sixth step, the semiconductor thin film below the second insulating film is crystallized by irradiating the light from above the second insulating film.
A method for manufacturing a thin film semiconductor device according to claim 1. Forming the amorphous semiconductor thin film in the fourth step;
And a step of crystallizing the semiconductor thin film between the sixth step and the seventh step.
A method for manufacturing a thin film semiconductor device according to claim 1. Forming the crystallized semiconductor thin film in the fourth step;
A method for manufacturing a thin film semiconductor device according to claim 1. Before the irradiation of the light beam, a product of an absorption coefficient of the second insulating film and a film thickness of the second insulating film is larger than 1,
The method for manufacturing a thin film semiconductor device according to claim 1. After the irradiation of the light beam, a product of an absorption coefficient of the second insulating film and a film thickness of the second insulating film is 1 or less.
The method for manufacturing a thin film semiconductor device according to claim 1. In the sixth step, the second insulating film is mineralized by irradiation with the light beam,
The method for manufacturing a thin film semiconductor device according to claim 1. The mineralization occurs when a light reaction or a thermal reaction proceeds in the second insulating film by the light beam.
A method for manufacturing a thin film semiconductor device according to claim 8. A substrate,
A gate electrode formed on the substrate;
A first insulating film formed on the gate electrode;
A crystalline semiconductor thin film formed on the first insulating film;
A source electrode and a drain electrode formed above the crystalline semiconductor thin film;
A second insulating film formed on the crystalline semiconductor thin film,
The second insulating film is formed by irradiating the precursor of the second insulating film with the light beam,
The transmittance of the second insulating film with respect to the light beam is higher after the light beam irradiation than before the light beam irradiation,
Thin film semiconductor device. The transmittance of the second insulating film with respect to the light beam is less than 37% before irradiation with the light beam, and is 37% or more after irradiation with the light beam.
The thin film semiconductor device according to claim 10. The precursor is composed of an organic material,
The second insulating film is one in which the organic material is mineralized by irradiation with the light beam.
The thin film semiconductor device according to claim 10 or 11. The product of the absorption coefficient of the second insulating film and the thickness of the second insulating film before the irradiation of the light beam is greater than 1,
The thin film semiconductor device according to any one of claims 10 to 12. The product of the absorption coefficient of the second insulating film and the thickness of the second insulating film after irradiation with the light beam is 1 or less;
The thin film semiconductor device according to any one of claims 10 to 12. Furthermore, it has an interface layer containing carbon formed between the crystalline semiconductor thin film and the second insulating film,
The concentration of carbon contained in the interface layer is at least 50 times the concentration of carbon as an impurity contained in the crystalline semiconductor thin film.
The thin film semiconductor device according to any one of claims 10 to 14. The concentration of carbon contained in the interface layer is 5 × 10 ²⁰ (atoms / cm ³ ) or more.
The thin film semiconductor device according to claim 15. The interface layer includes sulfur;
The thin film semiconductor device according to claim 15 or 16. The concentration of sulfur contained in the interface layer is at least 100 times the concentration of sulfur as an impurity contained in the crystalline semiconductor thin film.
The thin film semiconductor device according to claim 17. The concentration of sulfur contained in the interface layer is 5 × 10 ¹⁹ (atoms / cm ³ ) or more.
The thin film semiconductor device according to claim 17. The specific resistance of the interface layer is 2 × 10 ⁶ (Ω · cm) or more.
The thin film semiconductor device according to any one of claims 15 to 19. The thickness of the interface layer is 1 nm or more and 5 nm or less.
The thin film semiconductor device according to any one of claims 15 to 20.

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