JP2002270843A - Manufacturing method of thin-film transistor, activation of impurity and thin-film transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect an organic polymer substrate from damages even if a semiconductor laser is irradiated with a laser beam, in order to activate impurity-doped into a semiconductor layer. SOLUTION: An impurity is doped into the semiconductor layer 3 formed on the organic polymer substrate 1, and the impurity of the semiconductor layer 3 is activated by irradiating the semiconductor layer 2 with an energy beam, such as from Ar ion laser or copper vapor laser, of which energy absorption at the organic polymer substrate 1 is low such as not to give damages to such an organic polymer substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a thin film transistor for forming a semiconductor layer on an organic polymer substrate and activating an impurity introduced into the semiconductor layer, a method of activating the impurity, and a thin film transistor. In particular, the present invention relates to a manufacturing technique for forming an active layer of a thin film transistor without damaging a low heat resistant substrate.

[0002]

2. Description of the Related Art Thin film transistors using polycrystalline silicon as a channel (TFT: ThinFilm Tra)
An active matrix type liquid crystal display device that employs an N.sub.sistor as a switching element and a peripheral driving circuit has attracted attention. This is a reflection type, a large area, and a high-level structure by forming a thin film transistor array in which a large number of input / output elements with a small thickness for changing the liquid crystal arrangement are arranged on a substrate plane on an inexpensive amorphous glass substrate. This is because there is a possibility that a high-definition, high-quality and inexpensive panel display (for example, a flat television) can be realized.
As a condition required for the substrate of the liquid crystal screen, a substrate made of a low-cost material, in order to reduce the cost of the substrate by increasing the screen size of the liquid crystal without impairing the light transmittance as compared with the conventional substrate, or There is a demand for a technique for forming a thin film transistor made of polycrystalline silicon on an organic polymer substrate having excellent mechanical strength and light weight when used for a screen of a portable device.

On the other hand, semiconductors made of polycrystalline silicon (non-single-crystal crystalline silicon) such as polycrystalline silicon (poly-Si) or microcrystalline silicon (μc-Si)
It has a feature that the mobility of carriers is about 10 to 100 times larger than that of a semiconductor made of amorphous silicon, and has extremely excellent characteristics as a constituent material of a switching element. As described above, a thin film transistor using polycrystalline silicon as an active layer can operate at high speed. In recent years, various types of logic circuits, multiplexers using the same, EPROMs, EEPROMs, CCDs, RAMs, liquid crystal display devices, and electroluminescent devices have recently been developed. Attention has also been focused on switching elements that constitute driving circuits of sense display devices and the like.

By the way, in the process of manufacturing a thin film transistor using polycrystalline silicon, when thermal diffusion was mainly used to diffuse semiconductor impurities,
Although high-temperature processing up to 1200 ° C. has been used in the process, the current maximum heat treatment temperature is about 900 ° C., and the lowering of the manufacturing process is steadily proceeding. However,
In this temperature range, it is necessary to use quartz glass or the like having excellent heat resistance as an insulating substrate for manufacturing a thin film transistor even as the process temperature is reduced.

However, with the increase in the screen size of the liquid crystal display, it is necessary to use a relatively heat-resistant organic polymer substrate which can lower the process temperature and reduce the cost as compared with a conventional glass substrate. Are also being considered. The deformation temperature of the organic polymer substrate is at most 200 ° C. even when formed of a heat-resistant material.
About 250 ° C. Therefore, when the substrate is formed of an organic polymer, all the processes must be performed at a lower temperature condition of about 200 ° C. or lower than the conventional one.

Here, a conventional method for manufacturing a thin film transistor will be described. Generally, the following manufacturing process is known. First, on a substrate such as a quartz glass substrate or an organic polymer substrate, an insulating layer made of a SiO ₂ film, a SiNx film, or a laminated film thereof is formed at a temperature lower than the heat resistant temperature of the substrate.

Next, an amorphous silicon film is formed on the substrate by, for example, a method of depositing a thin film by using a plasma CVD method by mixing hydrogen or helium with silane gas. Next, a polycrystalline silicon thin film is formed by, for example, a method of crystallizing the amorphous silicon film. One of the methods for crystallizing this deposited thin amorphous silicon film
One known method uses electric furnace annealing or infrared annealing. In this case, the substrate itself needs to be heated to a relatively high temperature of 600 ° C. or higher, and when an organic polymer substrate having low heat resistance is used, This causes deformation and distortion of the substrate.

A method of irradiating an excimer laser for recrystallization is also known. An amorphous silicon film is once formed, and the amorphous silicon film is irradiated with an excimer laser to crystallize the film with the excimer laser. Promote the conversion. For example, XeCl
In the case of an excimer laser, the emission wavelength is 308 nm and its absorption coefficient is about 10 ⁶ cm ⁻¹ , so that it is absorbed in a region about 10 nm from the surface of the amorphous silicon thin film, and the temperature of the substrate almost rises. Without
The vicinity of the surface of the amorphous silicon thin film is crystallized. For this reason, it is particularly preferable to use a substrate made of a material having a low heat-resistant temperature.

Next, a gate insulating film made of a SiO ₂ film or the like is formed on the silicon film which has been made into a polycrystalline state by recrystallization at a temperature lower than the heat resistant temperature of the substrate, and a gate electrode is formed on the gate insulating film. Further, at the time of forming the gate electrode or before or after the formation of the gate electrode, isolation between elements for separating an element formation region including a channel region from another element formation region is performed. Next, impurities are introduced into the polycrystalline silicon film using the gate electrode and the like as a mask, and the polycrystalline silicon film into which the impurities are introduced is activated. Examples of the activation method include a lamp annealing method and a laser annealing method by irradiating a laser beam. Finally, a protective film such as a SiO ₂ film or a SiNx film is formed, and the source, the drain, and the gate are formed. The required thin film transistor is formed by forming the extraction electrode of the electrode.

[0010]

By the way, when activating impurities in a polycrystalline silicon film which is a semiconductor layer into which impurities are introduced, the method using lamp annealing raises the temperature of the substrate simultaneously with the activation. Therefore, especially in an organic polymer substrate having a low heat-resistant temperature, the substrate is deformed or distorted.

On the other hand, in activation using an excimer laser, laser annealing is performed only on the surface side of the polycrystalline silicon film, so that the temperature rise of the substrate is suppressed. However, when irradiating a semiconductor layer such as a polycrystalline silicon film with an excimer laser, the excimer laser reaches the substrate because element isolation has already been performed. When the substrate is made of a material that absorbs an excimer laser, such as an organic polymer substrate, the bonding of the polymer is broken by the light or heat of the excimer laser, and the substrate is damaged and the substrate itself is deteriorated.

In view of the above technical problems, the present invention provides a method for manufacturing a thin film transistor on a low heat-resistant organic polymer substrate by activating impurities in a semiconductor layer without damaging the organic polymer substrate. It is an object to provide a method of manufacturing a thin film transistor to be converted, a method of activating impurities, and a thin film transistor.

[0013]

In order to solve the above-mentioned problems, a method of manufacturing a thin film transistor according to the present invention comprises the steps of: introducing an impurity into a semiconductor layer formed on an organic polymer substrate; Irradiating the semiconductor layer with a laser beam whose energy absorption is low enough not to damage the organic polymer substrate to activate impurities in the semiconductor layer.

When activating impurities in the semiconductor layer, a laser beam having a low energy absorption is used so as not to damage the organic polymer substrate. When the laser is irradiated, the energy of the laser beam is absorbed by the semiconductor layer. At the same time, the absorption at the organic polymer substrate can be kept low.

In the method for activating an impurity according to the present invention, the step of introducing the impurity into a semiconductor layer formed on the organic polymer substrate may include the steps of: A step of irradiating the semiconductor layer with a laser beam that is low enough not to apply the light to activate the impurities in the semiconductor layer.

According to the impurity activation method of the present invention, as in the above-described method of manufacturing a thin film transistor of the present invention, a laser beam having low energy absorption is used so as not to damage the organic polymer substrate. At the time of laser irradiation, the energy of the laser beam is absorbed by the semiconductor layer, and at the same time, the absorption by the organic polymer substrate can be suppressed low.

Furthermore, in the thin film transistor of the present invention, impurities are introduced into a semiconductor layer formed on an organic polymer substrate, and the energy absorption in the organic polymer substrate is so low as not to damage the organic polymer substrate. By irradiating the semiconductor layer with a beam, impurities in the semiconductor layer are activated.

Similar to the above-described method of manufacturing the thin film transistor of the present invention, the thin film transistor of the present invention uses a laser beam having a low energy absorption so as not to damage the organic polymer substrate. Can be kept low.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a thin film transistor according to the present invention will be described below with reference to FIGS.

First Embodiment First, as shown in FIG. 1A, an organic polymer substrate 1 made of a synthetic resin material is used as a substrate. Examples of the organic polymer substrate 1 include polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polycarbonate, polyolefins such as polypropylene, polyphenylene sulfides such as polyphenylene sulfide, polyamides, aromatic polyamides, and polyether ketones. For example, a resin substrate having relatively excellent heat resistance, such as a polyethylene terephthalate resin or a polyether sulfone resin, can be used. The thickness of the organic polymer substrate 1 is, for example, 200 μm.
It is said.

An insulating layer 2 is formed on the organic polymer substrate 1 in advance as a thermal buffer layer for relaxing thermal stress. As the insulating layer 2, an inorganic material of SiO ₂
Film, SiNx film, etc., for example, 100
It is preferable to form a film with a thickness of 400 nm. In the present embodiment, the organic polymer material constituting the organic polymer substrate 1 is, for example, polyether sulfone (PES) (heat resistant temperature: 20
0 ° C.) or polyethylene terephthalate (PET) (heat-resistant temperature: 100 ° C.), so that the organic polymer substrate 1 is placed on the organic polymer substrate 1 at a temperature not exceeding the heat-resistant temperature of the organic polymer substrate 1, preferably at room temperature. The insulating layer 2 is formed by a method such as a PVD method (physical vapor deposition method) by a sputtering method or the like capable of forming the insulating layer 2. As an example, an SiO ₂ film is formed as the insulating layer 2 to a thickness of about 300 nm.

Next, in an inert gas such as helium gas, a semiconductor layer 3a is formed on the entire upper surface of the organic polymer substrate 1 on which the insulating layer 2 is formed. The semiconductor layer 3a is, for example, a thin amorphous silicon film, and is formed by depositing an amorphous silicon film to a thickness of about 30 nm by a sputtering method. At this time, the semiconductor layer 3a is formed at a temperature equal to or lower than the substrate temperature at which the film was formed in the previous step so as not to thermally deteriorate the organic polymer substrate 1 and the insulating layer 2.

Next, in order to recrystallize the semiconductor layer 3a, the entire surface of the semiconductor layer 3a is irradiated with a laser from above. The laser is an ultraviolet pulse laser beam such as an excimer laser, for example, XeCl (wavelength 308 n).
m), KrF (wavelength 248 nm), ArF (wavelength 193)
nm), XeF (wavelength 351 nm), or the like, or an Ar ion laser (wavelength 51
4 nm), copper vapor laser (wavelength 511 or 578 n)
m). The semiconductor layer 3a is recrystallized by laser annealing by laser irradiation to form a semiconductor film 3b made of a polycrystalline silicon film as shown in FIG. 1B. Note that a so-called quasi-single-crystal film may be formed as the semiconductor film 3b. This quasi-single crystal has a crystal structure similar to that of a single crystal, and is composed of a plurality of almost single crystal grains made of a semiconductor, and these crystal grains are preferentially oriented in one plane direction. The crystal grains adjacent to each other are substantially lattice-matched to each other at least at a part of the grain boundary. Regarding the crystal structure of the quasi-single crystal, a manufacturing method thereof is disclosed in Japanese Patent Application Laid-Open No. H11-145056.

When these lasers are irradiated, since the amorphous semiconductor layer 3a is formed on the entire upper surface of the insulating layer 2, it is almost completely absorbed by the semiconductor layer 3a.
Only the semiconductor layer 3a is laser-annealed and crystallized. Therefore, no laser is irradiated to the organic polymer substrate 1, and no damage to the substrate occurs at this stage.

As shown in FIG. 1C, the semiconductor layer 3b
Is etched into a predetermined shape, and a gate insulating film 4 is formed on the semiconductor layer 3c from which the elements are separated. Gate insulating film 4
Is formed of, for example, a SiO ₂ film, a SiNx film, or a laminated film of these, and is formed to have a thickness of about 50 nm at a substrate temperature equal to or lower than the heat-resistant temperature of the organic polymer substrate 1. In the present embodiment, for example, a SiO
_Two films are formed. At this time, the film formation method includes reactive sputtering, plasma CVD, vapor deposition, and JVD (Je
t Vapor Deposition) or the like, and the entire surface of the semiconductor layer 3c may be plasma-oxidized or plasma-nitrided.

Next, as shown in FIG. 1D, in this embodiment, an Al electrode is formed to a thickness of 240 nm as the gate electrode 5 on the gate insulating film 4 on the semiconductor layer 3c. As the metal for forming the gate electrode, Al, Cu, Mo, Ta,
Ti, Cr, platinum, ITO, or the like may be used. Also,
The gate electrode may be a polycrystalline silicon film doped with impurities at a high concentration, a stacked film of highly doped polycrystalline silicon and a metal, or an alloy film of the above-described materials. After the formation of the gate electrode 5, the semiconductor layer 3c may be formed into a required pattern by performing etching for element isolation, or the semiconductor layer 3c and the gate may be formed after the formation of the semiconductor layer 3c and the gate insulating film 4. The insulating film 4 may be etched together to perform patterning for element isolation.

Next, as shown in FIGS. 2A and 2B, using the gate electrode 5 as a mask, a source / drain region is formed by ion implantation or the like into the semiconductor layer 3c. Inject impurities. The ion implantation is performed by, for example, depositing atoms of group III boron and group V phosphorus activated in a high-density plasma on the substrate and simultaneously implanting them with low energy and shallowly. Impurities into the semiconductor layer 3
C can be introduced shallowly to form a pn junction.

In order to activate the impurities implanted in the source / drain formation region, activation has been performed by lamp annealing or excimer laser in the conventional manufacturing method. However, in the case of lamp annealing, there is a problem that the temperature of the substrate is raised to a temperature higher than the heat resistance temperature of the organic polymer substrate 1. In the method using the excimer laser irradiation, not only the semiconductor layer 3e but also the organic polymer substrate 1 The excimer laser is irradiated to the substrate, and as a result, the bond of the organic material is cut or abrasion occurs, thereby damaging the substrate. Therefore, in the present embodiment, FIG.
2 (c) and FIG. 2 (d), by irradiating an Ar ion laser, a copper vapor laser, or the like, which is absorbed by the semiconductor layer 3e into which the impurities are implanted and is not absorbed by the organic polymer substrate 1. Activate impurities. Since the laser photon energy of these lasers is smaller than the bond dissociation energy of the organic polymer material constituting the organic polymer substrate 1, the laser is hardly absorbed by the organic polymer substrate 1 and is hardly damaged by ablation or the like.

Here, as specific examples in which the energy of the irradiated laser beam is hardly absorbed by the substrate, polyether sulfone (PES), polyethylene terephthalate (PET), polyethylene naphthalate (PE)
The energy absorptivity when the laser beam is irradiated to N) is calculated. The data used to calculate the energy absorption is the transmittance, the refractive index of each material, and the reflectance.
First, FIG. 6 shows the measured values of the transmittance with respect to the wavelength under the condition that the surface of each organic polymer material is irradiated with a laser beam perpendicularly. Ar ion laser (wavelength 514 nm), copper vapor laser (wavelength 511, 5
For a laser beam having a wavelength exceeding about 500 nm (e.g., 78 nm), the energy transmittance of each of the above organic polymer materials exceeds about 90%, whereas an excimer laser (wavelength of 308 nm) has about 1%. Excimer laser beam has a much higher energy absorption rate by each of the above organic polymer materials than Ar ion laser beam and copper vapor laser beam, and the substrate is easily damaged by ablation. Would.

Next, the reflectance R of each organic polymer material is calculated. The refractive index of each of the above organic polymer materials is PES, P
ET and PEN are 1.66, 1.66, and 1.75 in the order, and light is introduced from the air side into the material having the refractive index n when the air is in contact with the material having the refractive index n in a plane. Formula R = ((n-1) for calculating the reflectance R used for normal incidence
/ (N + 1)) ² was used to calculate the reflectance when the organic polymer material was irradiated with a laser beam. as a result,
The reflectance of the substrate composed of the above organic polymer material is PE
The order of S, PET and PEN is 6.1, 6.1, 7.4.

Based on the above results, the energy absorptivity of each of the above organic polymer materials when a laser beam having a wavelength of about 500 nm or more is irradiated is calculated as shown in FIG.
0.9, 2.9, 2.6% in the order of ES, PET, PEN
And the energy amount of the laser beam substantially absorbed by the organic polymer substrate is estimated to be about 2% at the maximum.
It is estimated to be a degree. The amount of energy absorbed when irradiating a substrate made of an organic polymer material with an Ar ion laser beam or a copper vapor laser beam is small,
Substantially no substrate damage occurs.

Therefore, the impurities implanted in the semiconductor layer 3e as the source / drain formation region can be activated without damaging the substrate. The pulse condition of the laser that does not damage the organic polymer substrate 1 is preferably a pulse width of about 100 picoseconds or more and about 500 nanoseconds or less. This is because when the pulse width is smaller than about 100 picoseconds, sufficient activation cannot be performed, and a pulse width exceeding about 500 nanoseconds has a problem on the substrate and the like.

The Ar ion laser has a visible range (450 n).
m to 530 nm) in the ultraviolet region (270 nm to 3 nm).
60 nm) and has about 10 or more oscillation lines. Among these, a large output is obtained at wavelengths of 488 nm and 514 nm.
Are two transitions. Further, there is also known an apparatus which applies an axial magnetic field and focuses discharge plasma by Lorentz force in order to maintain high current density and reduce heating of a tube wall due to electron collision. A commercially available water-cooled Ar ion laser has an output of about 10 W in a multi-line (multi-wavelength) and about 2 W in a single line.
You can get up to about W. On the other hand, in the case of a small device, 10 to 100 mW can be obtained by air cooling.

Copper vapor laser (CVL: Copper)
Vapor Laser has an oscillation wavelength of 511 nm or 578 nm, and is one of the pulse lasers that can be obtained with high output and relatively high efficiency in the visible region. As a mechanism of the copper vapor laser, after filling an inert gas such as He or Ne as a buffer gas, a high-voltage pulse is applied between the cathode and the anode, and copper vapor is generated using heat generated by the discharge. This copper vapor is introduced into the laser tube at 10 ¹⁴ to 10 ¹⁶
It is uniformly distributed at a density of n / cm ³ (n is the number of atoms) and emits light having a wavelength specific to copper metal by being excited by free electrons in discharge plasma.

Although different from the present embodiment, the above-mentioned A
It is known that an r ion laser beam and a copper vapor laser beam are used for crystallization of an amorphous silicon film in a manufacturing process of a solar cell or a thin film transistor used for a solar cell. In this use case, PE
An amorphous silicon film is formed to a thickness of 200 to 400 nm by a CVD method, and after reducing the hydrogen density contained in the film to about 3% by annealing, an Ar ion laser beam (wavelength of 514 nm) or copper vapor is used. By irradiating the amorphous silicon film with a pulse beam of a laser beam (wavelengths of 511 nm and 578 nm), a high-quality polycrystalline silicon thin film can be formed in a shorter time than crystallization by heat treatment (for example, Solid). Sta
te Phenomena Vol. 67-68 (19
99) pp. 187-192).

After the impurities are activated by using an Ar ion laser or a copper vapor laser without damaging the substrate, the organic polymer substrate 1 is preferably used as shown in FIG. Under a film formation condition of about 100 ° C. or less that does not cause damage, a SiO ₂ film, SiNx is formed by a sputtering method or the like.
A protective film 6 made of a film or a laminated film thereof is formed on the gate insulating film 4 and the gate electrode 5, and a contact hole for the source and drain regions 3f is formed in the protective film 6 and the gate insulating film 4. 7 and a drain electrode 7 are formed. Similarly, a contact hole with the gate electrode 5 is formed, and a gate lead electrode 8 is formed.

As described above, according to the method for manufacturing a thin film transistor of the present embodiment, the energy absorption in the organic polymer substrate 1 having a relatively long wavelength such as an Ar ion laser or a copper vapor laser damages the organic polymer substrate 1. Since a laser that is low enough not to cause the impurity is used, the impurities implanted in the semiconductor layer 3e can be activated without damaging the substrate.

Further, by activating the impurities with a laser such as an Ar ion laser or a copper vapor laser, the treatment can be performed in a relatively short time, and compared with the case where electric furnace annealing or the like is used. The productivity can be improved.

[Second Embodiment]

In this embodiment, a so-called LIMPID (Laser-Induced Melting of Predeposi
ted Impurity Doping (Laser Induced Melting Predeposited Impurity Doping) is an example of applying a method, in which impurities are attached to the surface of a semiconductor layer, and then laser irradiation is performed without damaging the substrate. This is an example of activating impurities. The method of manufacturing the thin film transistor according to the present embodiment will be described in the order of steps with reference to FIGS.

The so-called LIMPID method is a method in which an impurity gas is ionized, impurity ions are adsorbed on the surface of the semiconductor thin film, and then dissolved in the film by an excimer laser, and hydrogen is not taken into the film. In addition, it is most suitable for a self-alignment process, and has attracted attention together with its suitability for a low-temperature process (Japanese Patent Laid-Open No. 61-13 / 1986).
Nos. 8131, 62-002531, 62-26419, and 9-293
No. 878).

First, as shown in FIG. 3A, an organic polymer substrate 11 made of a synthetic resin material is used as a substrate. Examples of the organic polymer substrate 11 include polyesters such as polyethylene terephthalate, polyethylene naphthalate and polycarbonate, polyolefins such as polypropylene, polyphenylene sulfides such as polyphenylene sulfide, polyamides, aromatic polyamides, and polyether ketones. For example, a resin substrate having relatively excellent heat resistance, such as polyethylene terephthalate (PET) resin or polyethersulfone (PES) resin, can be used. The thickness of the organic polymer substrate 11 is, for example, 200 μm.
It is said.

Next, the insulating layer 12 is formed on the organic polymer substrate 11.
Is formed, and a semiconductor layer 13a composed of an amorphous silicon film or the like is formed on the insulating layer 12. In this embodiment, an SiO ₂ film is formed as the insulating layer 12 to a thickness of 300 nm by a sputtering method.
As 3a, an amorphous silicon film is formed to a thickness of 30 nm by sputtering in helium gas.

Next, as shown in FIGS. 3A and 3B, an ultraviolet pulse laser beam such as an excimer laser, for example, XeCl (wavelength 308 nm), Kr
F (wavelength 248 nm), ArF (wavelength 193 nm), X
Laser annealing is performed by irradiating the entire surface of the semiconductor layer 13a with eF (wavelength 351 nm), Ar ion laser (wavelength 514 nm), copper vapor laser (511 nm or 578 nm), or the like. Recrystallization is performed by this laser beam irradiation, and a semiconductor layer 13b composed of a polycrystalline silicon layer is formed. This pulse laser beam is almost completely absorbed by the amorphous silicon film forming the semiconductor layer 13a and is not irradiated on the organic polymer substrate 11, so that the organic polymer substrate 11 is not damaged by ablation or the like.

Next, the semiconductor layer 13b is etched into a predetermined shape, and a gate insulating film 14 is formed on the separated semiconductor layer 13c as shown in FIG. The gate insulating film 14 is, for example, a SiO ₂ film or a SiNx film,
Alternatively, it is formed of a laminated film or the like of these, and is formed to have a thickness of about 50 nm at a substrate temperature equal to or lower than the heat-resistant temperature of the organic polymer substrate 1. In the present embodiment, for example, a film thickness of about 5
A 0 nm SiO ₂ <film is formed. At this time, a film forming method includes a reactive sputtering method, a plasma CVD method, a vapor deposition method, and a JVD method (Jet Vapor Deposition).
on) or the like, and the entire surface of the semiconductor layer 3c may be plasma-oxidized or plasma-nitrided.

Next, as shown in FIG. 3D, in this embodiment, an Al electrode is formed to a thickness of 240 nm as the gate electrode 15 on the gate insulating film 14 on the semiconductor layer 13c.
As the metal for forming the gate electrode, Al, Cu, Mo,
Ta, platinum, ITO, or the like may be used. After the formation of the gate electrode 15, etching for element isolation may be performed to form the semiconductor layer 13c into a required pattern. After the formation of the gate electrode 15, the semiconductor layer 13c may be formed into a required pattern by performing etching for element isolation, or after the formation of the semiconductor layer 13c and the gate insulating film 4, the semiconductor layer 13c and the gate The insulating film 14 may be etched together to perform patterning for element isolation.

Next, the gate electrode 15 is used as a mask.
Self-aligned etching, and thin film transistors
Etching only perpendicular to the substrate surface
The anisotropic selective etching in which
As described above, the region not masked by the gate electrode 15
The gate insulating film 14a is removed. Used for dry etching
The gas used is such that the gate insulating film 14a is made of SiO.₂in the case of
Is, for example, CF₄, CF ₄-H₂, C₂F₆, CH
F₃, C₃H₈Of SiNx, and
If the SF₆, CF₄, CF₄-O₂, NF₃, CH
₂F₂Use one of them.

Next, the gate electrode 15 of the semiconductor layer 13c is formed.
To expose the surface of the region where the source / drain is not masked. In the present embodiment, a plasma is generated in a mixed gas of CF ₄ and H ₂ , and the gate insulating film 14 a is etched by dry etching to form the semiconductor layer 1.
The surface of 3c is exposed.

Next, as shown in FIG. 4B, using the gate electrode 15 as a mask, a hydrogen gas
Alternatively, plasma is generated using a mixed gas using a mixed gas of an inert gas and a hydrogen gas, and doping ions are applied to the surface of the source / drain formation region of the semiconductor 13e in the region where the gate insulating film 14a is removed, as shown in FIG. Adsorb as shown in c). Here, when a p-type semiconductor is formed at the source / drain, B ₂ H containing boron which is a group III element is used.
_{6. In} the case of forming an n-type semiconductor, plasma is generated in a phosphine (PH ₃ ) gas containing phosphorus which is a group V element, and doping ions as impurities are attached to the exposed surface of the semiconductor layer 13e. In the present embodiment, for example, plasma irradiation is performed using a phosphine (PH ₃ ) gas to adsorb phosphorus ions on the surface of the semiconductor layer 13e.

In order to activate these impurities, an excimer laser is used here in the conventional method of manufacturing a thin film transistor. However, when the thin film transistor is formed on the organic polymer substrate 11, the semiconductor layer 13e is not present. The excimer laser is directly irradiated to the organic polymer substrate 11 other than the region where the organic polymer substrate 11 is to be damaged, and the organic polymer substrate 11 may be damaged. Therefore, in the present embodiment, as shown in FIG. 4D, the semiconductor layer 13e (which may be polycrystalline silicon or germanium) or the surface portion 13f of the semiconductor layer 13e to which impurities are adsorbed is sufficiently absorbed, In addition, the organic polymer substrate 11 is irradiated with a laser beam such as an Ar ion laser or a copper vapor laser which is hardly absorbed.

By irradiating a laser beam such as an Ar ion laser or a copper vapor laser, as shown in FIG. 4E, impurities adsorbed on the surface of the semiconductor layer 13e are dissolved into the film. Activation is performed to activate impurities in the semiconductor layer 13g corresponding to a region where a source / drain is formed in a region not masked by the gate electrode 15. Since this laser is hardly absorbed by the organic polymer substrate 11 similarly to the first embodiment, the laser can activate the impurities in the semiconductor layer 13g without causing damage to the substrate.

Next, as shown in FIG. 4F, the surface of the gate electrode 15 and the surface of the semiconductor layer 13g in which the impurities are dissolved and the exposed surface of the insulating layer 12 are covered with an insulating film made of a SiO ₂ film or a SiNx film. Then, a source and drain electrode 17 is formed by making holes from the source and drain electrodes, a contact hole is formed in the insulating film on the gate electrode 15, and a gate lead electrode 18 is formed. Through the above steps, a thin film transistor is completed.

As described above, according to the method of manufacturing a thin film transistor of the present embodiment, the energy absorption in the organic polymer substrate 11 of a relatively long wavelength such as an Ar ion laser or a copper vapor laser can be reduced. Using a pulse laser that is low enough not to damage the
The impurities implanted in the semiconductor layer 13e can be activated without damaging the substrate.

Further, by activating the impurities with a laser such as an Ar ion laser or a copper vapor laser, the treatment can be performed in a relatively short time, and compared with the case where electric furnace annealing or the like is used. The productivity can be improved.

In this embodiment, diffusion and activation of impurities adsorbed on the surface of the semiconductor layer 13e by plasma processing into the film can be simultaneously advanced by a laser such as an Ar ion laser or a copper vapor laser.
A device excellent in reproducibility using the method can be formed.

When assembling an active matrix type display device as an active element substrate on which the thin film transistor is mounted, another insulating substrate on which a counter electrode is formed in advance is bonded to the insulating substrate via a predetermined gap. In addition, an electro-optical material such as a liquid crystal may be disposed in the gap. Also, although the semiconductor layer was described as an amorphous silicon film which is initially a polycrystalline silicon film by recrystallization,
The present invention is not limited to this, and a semiconductor layer formed of amorphous, polycrystalline, quasi-single crystal, single crystal, or a combination thereof may be used. Further, the semiconductor layer is not limited to Si, but may be S
iGe, Ge, SiC or a combination thereof may be used.

[0057]

The method of manufacturing a thin film transistor according to the present invention,
According to the impurity activation method and the thin film transistor, the energy beam which is absorbed by the semiconductor layer and not absorbed by the organic polymer substrate is irradiated while using the organic polymer substrate having low heat resistance. The impurities implanted and adsorbed in the region can be electrically activated, and at the same time, damage to the substrate can be suppressed.
Therefore, the possibility of manufacturing an electronic device using a low heat-resistant organic polymer substrate is expanded, and the cost and performance of various devices can be reduced.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view illustrating a process up to a gate electrode forming process in a first embodiment of a method of manufacturing a thin film transistor according to the present invention, and FIG. It is a process sectional view showing the place where
(B) is a process sectional view up to recrystallization of the semiconductor layer,
(C) is a process sectional view until a gate insulating film is formed.
(D) is a process sectional view until a gate electrode is formed.

FIGS. 2A and 2B are process cross-sectional views showing up to the completion of the thin-film transistor in the first embodiment of the method for manufacturing a thin-film transistor according to the present invention; FIG. Is a process cross-sectional view showing a state in which is implanted, (c) is a process cross-sectional view until laser irradiation, (d) is a process cross-sectional view until activation of an impurity, and (e) is each electrode. It is a process sectional view until formation.

FIG. 3 is a process cross-sectional view showing a process up to a gate electrode forming process in a second embodiment of the method of manufacturing a thin film transistor according to the present invention. FIG. 3 (a) shows a process of forming an insulating layer and a semiconductor layer on an organic polymer substrate. It is a process sectional view showing the place where
(B) is a process sectional view up to recrystallization of the semiconductor layer,
(C) is a process sectional view until a gate insulating film is formed.
(D) is a process sectional view until a gate electrode is formed.

FIG. 4 is a process cross-sectional view illustrating a process of manufacturing a thin film transistor according to a second embodiment of the present invention up to the completion of the thin film transistor. FIG. 4A is a process cross-sectional view up to a point where a semiconductor layer surface is exposed. (B) is a process cross-sectional view up to the step of depositing impurities by plasma, and (c) is
Is a process cross-sectional view showing a state where impurities are attached,
(D) is a process sectional view up to laser irradiation, and (e).
FIG. 4 is a process cross-sectional view until activation of impurities, and FIG. 4F is a process cross-sectional view until formation of each electrode.

FIG. 5 is a diagram showing the transmittance with respect to the wavelength of a laser beam when a substrate made of an organic polymer material is irradiated with the laser beam.

FIG. 6 is a table summarizing the transmittance, the reflectance, the refractive index, and the energy absorption when a substrate made of an organic polymer material is irradiated with a laser beam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic polymer substrate 2 Insulating layer 3a Amorphous silicon film 3b Polycrystalline silicon film 4 Gate insulating film 5 Gate electrode 6 Protective film 7 Source or drain electrode 8 Gate extraction electrode 11 Organic polymer substrate 12 Insulating layer 13a Amorphous Silicon film 13b Polycrystalline silicon film 14 Gate insulating film 15 Gate electrode 16 Insulating film 17 Source or drain electrode 18 Gate lead electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Setsuo Usui 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Junichi Sato 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) HJ01 HJ12 HJ13 HJ18 HJ23 NN03 NN23 NN24 NN34 PP03 PP04 QQ11

Claims (14)

[Claims] A step of introducing impurities into a semiconductor layer formed on an organic polymer substrate; and a step of applying a laser beam whose energy absorption in the organic polymer substrate is low enough not to damage the organic polymer substrate. A method for manufacturing a thin film transistor, comprising a step of irradiating a semiconductor layer with light to activate impurities in the semiconductor layer. 2. The method according to claim 1, wherein the semiconductor layer is processed into an element-isolated shape before the laser beam irradiation. 3. The laser according to claim 1, wherein the laser whose energy absorption in the organic polymer substrate is low enough not to damage the organic polymer substrate is an Ar ion laser or a copper vapor laser. Method for manufacturing thin film transistor. 4. The method of claim 3, wherein a pulse interval of the laser is about 100 picoseconds or more and about 500 nanoseconds or less. 5. The method according to claim 1, wherein the semiconductor layer is made of amorphous, polycrystalline, quasi-single-crystal, single-crystal, or a combination thereof. 6. The semiconductor layer is made of Si, SiGe, G
The method according to claim 1, wherein the method is configured by using e, SiC, or a combination thereof. 7. The method according to claim 1, wherein the semiconductor layer is formed by recrystallizing an amorphous layer. 8. The method according to claim 7, wherein the recrystallization is performed by irradiating a laser beam of an excimer laser. 9. The organic polymer substrate has a softening point of about 250.
The method according to claim 1, wherein the temperature is lower than or equal to ° C. 10. The organic polymer substrate, comprising: the semiconductor layer, an insulating layer covering the semiconductor layer, and an electrode metal layer serving as an electrode of the thin film transistor. 2. The method according to claim 1, further comprising a step of forming a film under each condition. 11. A step of introducing impurities into a semiconductor layer formed on an organic polymer substrate, and the step of applying a laser beam whose energy absorption in the organic polymer substrate is low enough not to damage the organic polymer substrate. Activating an impurity in the semiconductor layer by irradiating the semiconductor layer with an impurity. 12. The method according to claim 11, wherein the laser is an Ar ion laser or a copper vapor laser. 13. An impurity is introduced into a semiconductor layer formed on an organic polymer substrate, and a laser beam whose energy absorption in the organic polymer substrate is low enough not to damage the organic polymer substrate is applied to the semiconductor layer. Irradiating the semiconductor layer to activate impurities in the semiconductor layer. 14. The thin film transistor according to claim 13, wherein the laser beam is an Ar ion laser or a copper vapor laser.