JP2005197576A - Method for manufacturing thin-film transistor, electro-optical device, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a poly-silicon film which has very high quality and contains less impurities. <P>SOLUTION: Formation of a semiconductor layer, measurement of the film thickness of the semiconductor layer, and crystallization thereof by light irradiation are carried out continuously, without being exposed to atmosphere, and the crystallization is carried out with an optimum light irradiation energy density found from the film thickness. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a thin film transistor, an electro-optical device including the thin film transistor as a switching element of a display pixel, and an electronic apparatus. It is about the method.

  Conventionally, semiconductor thin films such as polycrystalline silicon (poly-Si) have been widely used for thin film transistors (TFTs) and solar cells. In particular, poly-Si TFTs have high carrier mobility and can be manufactured on a transparent insulating substrate such as a glass substrate, so that switching elements such as liquid crystal display devices, liquid crystal projectors and organic EL display devices, or liquid crystal devices can be used. It is widely used as a circuit element of a driver for driving.

  As a method for producing a high-performance TFT on a glass substrate, a manufacturing method called a high-temperature process has already been put into practical use. Among TFT manufacturing processes, a process using a high temperature having a maximum temperature of about 1000 ° C. is generally called a high temperature process. The characteristics of the high-temperature process are that a relatively good quality polycrystalline silicon can be formed by solid phase growth of silicon, a good quality gate insulating layer can be obtained by thermal oxidation of silicon, and clean polycrystalline. This is the point that an interface between silicon and the gate insulating layer can be formed. Due to these characteristics, a high-performance TFT having high mobility and high reliability can be stably manufactured in a high-temperature process. However, in the high-temperature process, in order to crystallize the Si film by solid phase growth, a long-time heat treatment of about 48 hours at a temperature of about 600 ° C. is required. This is a very long process, and in order to increase the process throughput, a large number of heat treatment furnaces are inevitably required, and it is difficult to reduce the cost. In addition, quartz glass must be used as an insulating substrate with high heat resistance, so the substrate price is high and it is said that it is not suitable for large area.

On the other hand, a technique for lowering the process temperature and manufacturing a poly-Si TFT on an inexpensive large-area glass substrate is a technique called a low-temperature process. Among TFT manufacturing processes, a process for manufacturing a poly-Si TFT on a relatively inexpensive heat-resistant glass substrate under a temperature environment where the maximum temperature is approximately 600 ° C. or lower is generally called a low-temperature process. In a low temperature process, a laser crystallization technique for crystallizing a silicon film by using a pulse laser having an extremely short oscillation time is widely used. Laser crystallization is a technique that utilizes the property of crystallizing in the process of solidifying instantaneously by irradiating a silicon thin film on a substrate with high-power pulsed laser light. Recently, a technique for producing a large-area poly-Si film by scanning an amorphous silicon film on a glass substrate while repeatedly irradiating it with an excimer laser beam has been widely used. As the gate insulating layer, a silicon dioxide (SiO ₂ ) film can be formed on a large area substrate by a film forming method using plasma CVD. With these technologies, poly-Si TFTs can be fabricated on a large glass substrate that is currently several tens of centimeters on a side.

  However, what becomes a problem in this low-temperature process is impurities such as hydrocarbon introduced into the semiconductor layer (poly-Si) serving as an active layer. Generally, when manufacturing a low-temperature poly-si TFT using a laser crystallization technique, an apparatus for forming an amorphous silicon film is different from a laser crystallization apparatus. Therefore, after the amorphous silicon film is formed and taken out from the apparatus, the amorphous silicon surface is exposed to the atmosphere, and impurities such as hydrocarbon adhere to the amorphous silicon film surface. Before laser crystallization, the natural oxide film is generally removed with dilute hydrofluoric acid, etc., and at the same time, the hydrocarbon can be removed. However, the natural oxide film removal process and transport to the laser irradiation device are also performed in the atmosphere. Again, the hydrocarbon will adhere to the amorphous silicon surface again. These impurities form trap levels inside the semiconductor layer, cause a decrease in mobility and a high threshold voltage, and have a great adverse effect on characteristics. In order to solve such a problem, there is a method for preventing contamination of the poly-Si film by forming a semiconductor layer and performing laser crystallization without exposure to the atmosphere (see, for example, Patent Document 1). ).

  This method is a very effective means for preventing impurities from being mixed into the semiconductor layer, but has a serious problem. That is a problem that laser irradiation must be performed in a state where the thickness of the formed semiconductor layer is unknown. FIG. 2 is a diagram in which the crystallization ratio with respect to the film thickness when irradiated at the same laser irradiation energy density is measured by spectroscopic ellipsometry. From this figure, it can be seen that the optimum laser irradiation energy density for laser crystallization greatly depends on the film thickness. Even when the semiconductor layer is formed under exactly the same conditions, the film thickness varies. Therefore, in the above-described method, the laser is not necessarily irradiated under the optimum laser irradiation condition, and the crystallization state is greatly different for each substrate. That is, the TFT characteristics vary greatly from substrate to substrate.

JP-A-3-289140

  Therefore, in view of the above-described problems, the present invention performs semiconductor layer formation, semiconductor layer thickness measurement, and crystallization by light irradiation continuously without exposure to the atmosphere, and by performing crystallization with an optimal light irradiation energy density. , A manufacturing method of a thin film transistor that realizes improvement in characteristics of poly-Si TFT, and a manufacturing method that can reduce variation between substrates, and further, a high-performance electro-optical device and an electronic device using the same Gives technology to provide equipment.

  In order to solve the above problems, a method of manufacturing a thin film transistor according to the present invention includes a first step of forming a semiconductor layer serving as a channel portion on a substrate, a second step of measuring a film thickness of the semiconductor layer, and the substrate. In the method of manufacturing a thin film transistor, which includes a third step of transporting and a fourth step of crystallizing the semiconductor layer by light irradiation, the first step, the second step, the third step, and the fourth step are exposed to the atmosphere. It is characterized by being performed continuously.

  The first step and the second step are performed in the same atmosphere.

  Alternatively, the second step and the third step are performed in the same atmosphere.

  In order to solve the above problems, a thin film transistor manufacturing method of the present invention includes a first step of forming a semiconductor layer to be a channel portion on a substrate, a second step of transporting the substrate, and a film thickness of the semiconductor layer. In the method for manufacturing a thin film transistor, which includes a third step of measuring and a fourth step of crystallizing the semiconductor layer by light irradiation, the first step, the second step, the third step, and the fourth step are exposed to the atmosphere. It is characterized by being performed continuously.

  Further, the third step and the fourth step are performed in the same atmosphere.

  The film thickness of the semiconductor layer is measured by irradiating light perpendicular to the substrate.

  The electro-optical device according to the present invention includes a thin film transistor manufactured by any of the above-described methods as a driving element of a display pixel. As a result, the LCD or organic EL display device can be provided with a memory, a fingerprint sensor, and a circuit group having a calculation function, and a higher-performance display device can be provided.

  The electronic apparatus of the present invention includes the above electro-optical device. As such an electronic device, for example, a mobile phone, a video camera, a personal computer, a head mounted display, a projector, a fax machine, a digital camera, a portable television, a portable information terminal, an electronic notebook, a multi-function card, and the like are preferable.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a sectional view of a semiconductor thin film manufacturing process of the present invention.
(1. Formation of semiconductor layer)
In order to carry out the present invention, usually, a base protective film (101) is formed on a substrate (100) and a semiconductor thin film (102) is formed thereon. This series of forming methods will be described.

Examples of the substrate (100) to which the present invention can be applied include conductive materials such as metals, ceramic materials such as silicon carbide (SiC), alumina (Al ₂ O ₃ ), and aluminum nitride (AlN), fused quartz, glass, and the like. A transparent or non-transparent insulating material, a semiconductor material such as silicon or germanium wafer, and an LSI substrate processed therewith are possible. The semiconductor film is deposited directly on the substrate or via a base protective film, a lower electrode, or the like.

Examples of the base protective film (101) include an insulating material such as a silicon oxide film (SiO _x : 0 <x ≦ 2) and a silicon nitride film (Si ₃ N _x : 0 <x ≦ 4). When it is important to control impurities in a semiconductor film as in the case where a thin film semiconductor device such as a TFT is formed on a normal glass substrate, sodium (Na), potassium (K), etc. contained in the glass substrate are important. It is preferable to deposit the semiconductor film after forming the base protective film so that mobile ions do not enter the semiconductor film. In the case where a conductive material such as a metal material is used as a substrate and the semiconductor film must be electrically insulated from the metal substrate, a base protective film is naturally indispensable to ensure insulation. Further, when a semiconductor film is formed on a semiconductor substrate or an LSI element, an interlayer insulating film between transistors or wirings is also a base protective film.

For the base protective film, the substrate is first cleaned with an organic solvent such as pure water or alcohol, and then an atmospheric pressure chemical vapor deposition method (APCVD method), a low pressure chemical vapor deposition method (LPCVD method), or a plasma chemical vapor phase is formed on the substrate. It is formed by a CVD method such as a deposition method (PECVD method) or a sputtering method. When a silicon oxide film is used as the base protective film, the atmospheric pressure chemical vapor deposition method can be deposited using monosilane (SiH ₄ ) or oxygen as a raw material at a substrate temperature of about 250 ° C. to 450 ° C. In the plasma chemical vapor deposition method and the sputtering method, the substrate temperature is about room temperature to 400 ° C. The film thickness of the base protective film needs to be sufficient to prevent the impurity element from diffusing and mixing from the substrate, and its value is at least about 100 nm. Considering the variation between lots and substrates, the thickness is preferably about 200 nm or more, and if it is about 300 nm, the function as a protective film can be sufficiently achieved. In the case where the base protective film also serves as an interlayer insulating film such as a wiring connecting IC elements or wirings between them, the film thickness is usually about 400 nm to 600 nm. If the insulating film becomes too thick, cracks due to the stress of the insulating film occur. Therefore, the maximum film thickness is preferably about 2 μm. When it is necessary to consider productivity, the upper limit of the insulating film thickness is about 1 μm.

Next, the semiconductor thin film (102) will be described. As a semiconductor film to which the present invention is applied, silicon / germanium (Si _x Ge _1-x : 0 <x <1), silicon, etc., in addition to a single group IV semiconductor film such as silicon (Si) or germanium (Ge). carbide _{(Si x C 1-x:} 0 <x <1) and germanium carbide _{(Ge x C 1-x:} 0 <x <1) group IV element complexes of the semiconductor film such as gallium arsenide (GaAs ) And indium antimony (InSb), etc., a compound compound semiconductor film of a group 3 element and a group 5 element, or a compound compound semiconductor film of a group 2 element, such as cadmium selenium (CdSe), and a group 6 element, etc. is there. Or a silicon germanium gallium arsenide _{(Si x Ge y Ga z As} z: x + y + z = 1) and further went Naru complex compound semiconductor film or a phosphorus these semiconductor films (P), arsenic (As), antimony (Sb The present invention also applies to an N-type semiconductor film to which a donor element such as) is added, or a P-type semiconductor film to which an acceptor element such as boron (B), aluminum (Al), gallium (Ga), or indium (In) is added. Is adaptable. These semiconductor thin films are formed by a CVD method such as an APCVD method, an LPCVD method, or a PECVD method, or a PVD method such as a sputtering method or a vapor deposition method. In the case of using a silicon film as the semiconductor film, the LPCVD method can be deposited using disilane (Si ₂ H ₆ ) or the like as a raw material at a substrate temperature of about 400 ° C. to 700 ° C. In the PECVD method, deposition can be performed at a substrate temperature of about 100 ° C. to 500 ° C. using monosilane (SiH ₄ ) as a raw material. When the sputtering method is used, the substrate temperature is about room temperature to 400 ° C. The initial state (as-deposited state) of the semiconductor film deposited in this manner includes various states such as amorphous, mixed crystal, microcrystalline, and polycrystalline. It may be in a state. In the present specification, not only amorphous crystallization but also polycrystalline and microcrystalline recrystallization are all called crystallization. The thickness of the semiconductor film is suitably about 20 nm to 100 nm when it is used for a TFT.

  After forming the semiconductor layer, the thickness of the semiconductor layer is measured and laser crystallization is performed without exposing the substrate to the atmosphere. This makes it possible to prevent impurities such as hydrocarbons from adhering to the semiconductor thin film and diffusing into the semiconductor layer during laser crystallization. In addition, by measuring the film thickness, it is possible to calculate the optimum irradiation energy density in laser crystallization performed in the next process, and to improve the TFT characteristics and reduce the variation for each substrate. Further, by not exposing to the atmosphere, a natural oxide film is not formed on the semiconductor thin film, the etching process can be omitted, and the throughput can be significantly improved.

(2. Measurement of semiconductor layer thickness)
Here, the film thickness measurement will be described.

  For measuring the thickness of a thin film, spectroscopic ellipsometry (see FIG. 3), an optical interference type film thickness measuring device (see FIG. 4), and the like are currently used. In spectroscopic ellipsometry, light irradiated from a light source (300) with an angle θ (generally about 70 degrees) passes through a polarizing plate (301) to become linearly polarized light and is irradiated onto a thin film. Reflected light from the thin film is detected by a light receiving element (303) installed at an angle θ, the change in polarization characteristics of the reflected light is detected, and the light is dispersed and subjected to photoelectric conversion. The film thickness is determined from the parameters of amplitude reflectance and phase difference. Measure. Therefore, when the height of the thin film to be measured is shifted, the reflected light from the thin film is not introduced into the light receiving element, and thus the film thickness cannot be measured. That is, spectroscopic ellipsometry is a very sensitive measurement with respect to the height of the substrate, and it is necessary to provide the apparatus with a mechanism for adjusting the height, which increases the cost of the apparatus.

  On the other hand, the interference film thickness measuring device irradiates light perpendicularly to the substrate, and reflects the light reflected from the surface of the semiconductor layer, the interface between the semiconductor layer and the base protective film, and the interface between the base protective film and the substrate. The film thickness is obtained by measuring the interference phenomenon. Therefore, there is no restriction regarding the height of the substrate. Further, since the mechanism is very simple as an apparatus, it can be realized at a lower cost than spectroscopic ellipsometry. That is, it is desirable that the film thickness measuring apparatus provided in the present invention is an apparatus that is not limited by the height of the substrate, such as an optical interference type film thickness measuring apparatus.

  In order to reduce the manufacturing cost of the apparatus and the tact time during transport, the film thickness measuring apparatus does not provide a new measuring chamber, but a semiconductor forming chamber (see FIG. 5) or a light irradiation chamber (see FIG. 6). ) Or a transfer chamber (see FIG. 7).

  The installation position of the film thickness measuring device has different advantages in each of the semiconductor formation chamber, the transfer chamber, and the light irradiation chamber.

  When the semiconductor film formation chamber (500) is provided with a film thickness measuring device (501), the film thickness is measured after the semiconductor film is formed, and if the film is formed thinner than a desired film thickness, Processing is possible. Further, if the optical characteristics are significantly different from the original due to abnormal discharge of plasma or the like, it can be determined to be defective before being transferred to the laser irradiation chamber. However, in the case where the film forming chamber is provided with a film thickness measuring device, a mechanism that can be separated from the forming chamber is necessary to prevent the thin film measuring device from forming a thin film. For example, it is a mechanism such as a shutter (502) that separates the formation chamber from the measurement chamber.

  When the laser irradiation chamber (600) is equipped with a film thickness measuring device (601), the crystallinity is inspected from its optical characteristics by measuring the crystallized poly-si film after crystallization by laser irradiation. I can do it. However, even when the laser processing chamber is equipped with a film thickness measuring device, a mechanism that can be isolated from the forming chamber is necessary to prevent silicon slightly released by laser crystallization from adhering to the thin film measuring device. . For example, it is a mechanism such as a shutter (602) that separates the formation chamber and the measurement chamber.

  When the transfer chamber (700) is provided with a film thickness measuring device (701), there is no need to isolate the thin film forming device from the transfer chamber because a thin film is not formed and attached to the thin film measuring device. Have.

(3. Laser crystallization of semiconductor thin films)
Here, laser light will be described. It is desired that the laser light is strongly absorbed on the surface of the semiconductor thin film (102) and hardly absorbed by the insulating film (101) or the substrate (100) immediately below the laser light. Therefore, excimer laser, argon ion laser, YAG laser harmonic, etc. having a wavelength in the ultraviolet region or the vicinity thereof are preferable as this laser light. Further, in order to heat the semiconductor thin film to a high temperature and simultaneously prevent damage to the substrate, it is necessary to have a pulse output with a large output and a very short time. Therefore, excimer lasers such as a xenon chloride (XeCl) laser (wavelength 308 nm) and a krypton fluoride (KrF) laser (wavelength 248 nm) are most suitable among the above laser beams.

Next, the laser light irradiation method will be described with reference to FIG. The half width of the intensity of the laser pulse is an extremely short time of about 10 ns to about 500 ns. The laser irradiation is performed in a vacuum in which the substrate (800) is between room temperature (25 ° C.) and 400 ° C. and the background vacuum is about 10 ⁻⁴ Torr to 10 ⁻⁹ Torr. The single irradiation area of the laser irradiation is a square or rectangular shape with a diagonal of about 5 mm □ to about 60 mm □. A case where a beam capable of crystallizing, for example, a square area of 8 mm □ by one irradiation of laser irradiation will be described. After one laser irradiation (801) is performed at one place, the positions of the substrate and the laser are slightly shifted in the horizontal direction relatively (803). Thereafter, one laser irradiation (802) is performed again. By repeating this shot and scan continuously, it is possible to cope with a large area substrate. More specifically, the irradiation area is shifted from about 1% to about 99% for each irradiation (for example, 50%: 4 mm in the previous example). After first scanning in the horizontal direction (X direction), the scanning is then shifted by an appropriate amount (804) in the vertical direction (Y direction), and then again by a predetermined amount (803) in the horizontal direction, and this scanning is repeated thereafter. The first laser irradiation is performed on the entire surface of the substrate. Laser irradiation energy density of the first time is preferably between about 50 mJ / cm ² of about 600 mJ / cm ^2. After the first laser irradiation is completed, the second laser irradiation is performed on the entire surface as necessary. When the second laser irradiation is performed, the energy density is preferably higher than that of the first time, and may be between about 100 mJ / cm ^{2 and} about 1000 mJ / cm ² . The scanning method is the same as the first laser irradiation, and the square irradiation region is scanned by shifting an appropriate amount in the Y direction and the X direction. Furthermore, it is possible to perform the third or fourth laser irradiation with a higher energy density as required. When such a multi-stage laser irradiation method is used, it is possible to completely eliminate variations caused by the end of the laser irradiation region. The laser irradiation is performed at an energy density that does not damage the semiconductor film, not only in the multi-stage laser irradiation but also in the normal one-step irradiation. In addition to this, as shown in FIG. 9, the irradiation region shape may be a line shape (901) having a width of about 100 μm or more and a length of several tens of centimeters or more, and the crystallization may be advanced by scanning this line-shaped laser beam. . In this case, the overlap in the beam width direction for each irradiation is about 5% to 95% of the beam width. If the beam width is 100 μm and the overlap amount for each beam is 90%, the beam advances 10 μm for each irradiation, so that the same point receives 10 laser irradiations. Usually, in order to crystallize the semiconductor film uniformly over the entire substrate, at least about 5 times of laser irradiation is desired. Therefore, the overlap amount of the beam for each irradiation is required to be about 80% or more. In order to reliably obtain a highly crystalline polycrystalline film, it is preferable to adjust the overlap amount from about 90% to about 97% so that the same point is irradiated about 10 to 30 times. By using a line beam, it is possible to crystallize a wide area by scanning in one direction, so that an advantage is obtained that the throughput can be increased as compared with the above-described square beam.

Here, the formation of trap levels in a semiconductor thin film by laser irradiation will be described. Since the semiconductor thin film is melted and crystallized by laser irradiation, the temperature of the silicon film rises to 1400 ° C. or higher, and is then rapidly cooled at a rate of about 10 ¹⁰ K / s by thermal diffusion to the substrate. That is, melting and crystal growth are completed at most after 100 ns after laser irradiation. As can be easily inferred from this, the formation time of the crystal grain boundary is extremely short, so that silicon atoms cannot form a good bond with each other, resulting in a large amount of dangling bonds occurring at the crystal grain boundary. . These dangling bonds form trap levels. As a result, a trap level of 10 ¹⁸ cm ⁻³ or more is generated at the crystal grain boundary in high-speed crystal growth such as laser crystallization.

(4. Plasma treatment of semiconductor thin films)
In order to reduce the trap level due to dangling bonds, it is effective to perform hydrogen plasma treatment or oxygen plasma treatment (106) after laser crystallization. Further, performing these plasma treatments without exposure to the atmosphere after laser irradiation can eliminate the step of removing the natural oxide film with dilute hydrofluoric acid before performing the plasma treatment, leading to a reduction in tact time.

  Here, the plasma treatment will be described. Hydrogen or oxygen is introduced into the plasma processing chamber via a mass flow controller, and plasma discharge is performed on the entire surface of the substrate by parallel plate RF electrodes. The substrate temperature during the plasma treatment is desirably 200 ° C. to 400 ° C.

In the hydrogen plasma treatment, active hydrogen atoms, ions, and radicals are easily bonded to dangling bonds that cause trap levels. As a result, the dangling bonds are electrically inactivated and the trap levels can be effectively reduced. However, the hydrogen plasma treatment has the property of inactivating the trap level and simultaneously breaking the silicon bond to generate a dangling bond (that is, the trap level). Since the phenomenon of breaking the silicon bond appears more prominently as the RF power is higher, it is preferable to discharge the RF power with a low power of about 0.05 W / cm ² . In addition, hydrogen easily diffuses into the poly-si film in a short time and bonds with dangling bonds. Therefore, the processing time is preferably about 15 seconds to 1 minute.

  In the oxygen plasma treatment, the phenomenon of breaking the silicon bond as described above is not observed, and it is known that the oxygen bond is more effectively bonded to the dangling bond. Since oxygen has a lower diffusion coefficient into the poly-si film than hydrogen, the treatment time is longer than hydrogen plasma treatment, and is preferably about 5 to 20 minutes.

(5. Subsequent steps)
After performing the plasma treatment, an element isolation process is performed to electrically insulate the TFT elements from each other. A pattern is formed on the poly-Si film by photolithography, and then the poly-Si film is etched by dry etching. Here, care must be taken so that the shape of the edge after etching does not become wrinkled.

  Next, a gate insulating film (107) is formed using plasma CVD. There are parallel plate type RF discharge, ICP discharge, ECR discharge, and the like as discharge forms, and RF power supply, VHF, UHF power supply, and microwave source can be used as power supply.

Subsequently, a thin film to be the gate electrode (108) is deposited by the PVD method or the CVD method. This material has a low electric resistance and is desired to be stable to a heat process of about 350 ° C., and a high melting point metal such as tantalum, tungsten, or chromium is suitable. Further, when the source and drain are formed by ion doping, the thickness of the gate electrode is required to be about 700 nm in order to prevent hydrogen channeling. Among the refractory metals, tantalum is most suitable when it becomes a material that does not cause cracks due to film stress even if it has a film thickness of 700 nm. The thin film to be the gate electrode is patterned after deposition, and then impurity ions are implanted into the semiconductor film to form source / drain regions (109). At this time, since the gate electrode is a mask for ion implantation, the channel has a self-aligned structure formed only under the gate electrode. Impurity ion implantation uses an ion doping method in which hydride and hydrogen of an implanted impurity element are implanted using a mass non-separable ion implanter, and ion implantation in which only a desired impurity element is implanted using a mass separated ion implanter. Two types of law can be applied. As a source gas for the ion doping method, a hydride of an implanted impurity element such as phosphine (PH ₃ ) or diborane (B ₂ H ₆ ) having a concentration of about 0.1% to 10% diluted in hydrogen is used. When a CMOS TFT is formed, one of NMOS and PMOS is alternately covered with a mask using an appropriate mask material such as polyimide resin, and each ion implantation is performed by the method described above.

  Further, there is laser activation that irradiates an excimer laser or the like as an efficient method for activating impurities. This is a method of activating impurities by melting and solidifying doped poly-Si in the source and drain portions by laser irradiation through an insulating film.

  Next, an interlayer insulating film (110) is formed, a contact hole is formed on the source / drain, and a source / drain extraction electrode (111) and wiring are formed by a PVD method, a CVD method, or the like to complete the thin film transistor.

An embodiment of the present invention will be described with reference to FIG. In this example, a case where a film thickness measuring device is provided in the laser irradiation chamber will be described (see FIG. 6). Although the substrate and the base protective film used in the present invention are in accordance with the above description, 300 mm × 300 mm square general-purpose non-alkali glass (100) is used here as an example of the substrate. First, a base protective film (101) that is an insulating material is formed on a substrate (100). In this example, a silicon oxide film is deposited to a thickness of about 500 nm by a parallel plate plasma CVD method at a substrate temperature of 430.degree. Next, a semiconductor film (102) such as an intrinsic silicon film to be an active layer of the thin film transistor later is deposited. The thickness of the semiconductor film is about 50 nm. In this example, the film was deposited in the same chamber by the parallel plate plasma CVD method continuously with the deposition of the base protective film (101). After depositing the base protective film, evacuation and Ar filling are repeated twice, the inside of the chamber is replaced with Ar, and a gas such as O ₂ used in the base film is discharged from the chamber. Next, 100 sccm of silane (SiH ₄ ) as a source gas is flowed, and an amorphous silicon film (102) is deposited at a deposition temperature of 430 ° C. for 60 seconds. Next, the substrate is transferred to a heating chamber in a vacuum, and the substrate is heated at 490 ° C. for 10 minutes. As a result, the hydrogen content in the semiconductor film is 1 atm. %, And laser crystallization is possible.

Next, the substrate is taken out from the heating chamber and transferred to a laser irradiation chamber in a vacuum. First, the thickness of the conveyed substrate was measured by a light interference type film thickness measuring device (103). As a result, the film thickness of the amorphous silicon film (102) is 47.3 nm, and the optimum laser irradiation condition is 420 mJ / cm ² . After measuring the film thickness, the shutter (602) was closed to isolate the optical interference type film thickness measuring apparatus from the laser processing chamber. Next, laser light is irradiated. In this example, an xenon chloride (XeCl) excimer laser (wavelength: 308 nm) is irradiated. The intensity half width (half width with respect to time) of the laser pulse is 25 ns. The laser irradiation area was a line having a length of 150 mm and a width of 0.4 mm, and the energy density on the irradiated surface was 420 mJ / cm ² . Irradiation is repeated while the laser beams are overlapped 96.25% each (that is, 15 μm for each irradiation) and relatively shifted (see FIG. 9). In this way, the amorphous silicon of the entire substrate having a side of 300 mm is crystallized. Before taking the substrate out of the laser irradiation chamber, the gate valve (602) was opened, and the optical characteristics were again measured with an optical interference type film thickness measuring device. As a result, the crystallization rate of the laser crystallized poly-si film is 97.3%, and a film having excellent crystallinity can be formed.

Next, the substrate is set in a plasma processing chamber, and oxygen gas is introduced into the chamber. In this example, 99.999% oxygen gas was introduced from the mass flow controller, and the gas flow rate was 1000 sccm. The pressure in the chamber was adjusted to 1 torr. When the gas pressure in the chamber was stabilized, RF discharge was started, and the trap level in the laser crystallized poly-Si film was terminated. The substrate temperature was 350 ° C., and the input RF power was 0.15 W / cm ² . With the generated active species, the trap level of the poly-Si film was inactivated to a sufficiently low density in a processing time of 600 seconds.

  Next, etching was performed to separate the poly-si film.

Next, a gate insulating film is formed. Silane gas and oxygen gas are introduced into the chamber at a flow ratio of 1: 6, and the chamber pressure is adjusted to 2 × 10 ⁻³ (Torr). When the gas pressure in the chamber is stabilized, ECR discharge is started and film formation of the insulating film is started. The input microwave power was 1 kW, and the microwave was introduced from the introduction window parallel to the magnetic field lines. There is an ECR point at a position 14 cm from the introduction window. The film formation was performed at a film formation rate of 100 (nm / min.). Thereby, a gate insulating film (107) was formed to 100 nm.

Subsequently, a thin film to be the gate electrode (108) is deposited by a PVD method, a CVD method or the like. Usually, since the gate electrode and the gate wiring are made of the same material and in the same process, it is desirable that this material has a low electric resistance and is stable to a heat process of about 350 ° C. In this example, a tantalum thin film having a thickness of 600 nm is formed by sputtering. The substrate temperature when forming the tantalum thin film is 180 ° C., and an argon gas containing 6.7% nitrogen gas is used as the sputtering gas. The tantalum thin film thus formed has an α structure and a specific resistance of about 40 μΩcm. The thin film to be the gate electrode is patterned after deposition, and then impurity ions are implanted into the semiconductor film to form the source / drain region (109) and the channel region. At this time, since the gate electrode is a mask for ion implantation, the channel has a self-aligned structure formed only under the gate electrode. As a source gas for the ion doping method, a hydride of an implanted impurity element such as phosphine (PH ₃ ) or diborane (B ₂ H ₆ ) having a concentration of about 0.1% to 10% diluted in hydrogen is used. In this example, aiming at NMOS formation, an ion doping apparatus is used to implant phosphine (PH ₃ ) having a concentration of 5% diluted in hydrogen at an acceleration voltage of 100 keV. The total ion implantation amount including PH ₃ ⁺ and H ₂ ⁺ ions is 1 × 10 ¹⁶ cm ⁻² .

  Next, an interlayer insulating film (110) is deposited, contact holes are formed on the source / drain, source / drain extraction electrodes (111) and wiring are formed by PVD or sputtering, thereby completing the thin film transistor. .

  The thin film transistor obtained by the manufacturing method of the present invention can be applied to various electronic devices including an electro-optical device. 10 and 11 show examples of electronic apparatuses to which the electro-optical device can be applied. FIG. 10 shows an application example to a cellular phone. The cellular phone (1000) includes an antenna unit (1001), an audio output unit (1002), an audio input unit (1003), an operation unit (1004), and the electric of the present invention. An optical device (10) is provided. As described above, the electro-optical device (10) of the present invention can be used as a display unit of the mobile phone (1000). FIG. 11 shows an application example to a video camera. The video camera (1100) includes an image receiving unit (1101), an operation unit (1102), and the electro-optical device (10) of the present invention. As described above, the electro-optical device of the present invention can be used as a finder or a display unit. In addition, the present invention can be applied to portable personal computers, head mounted displays, rear projectors, and front projectors. As described above, the electro-optical device of the present invention can be used as an image display source.

  The electro-optical device (10) of the present invention is not limited to the above example, and can be applied to any electronic apparatus to which an active matrix electro-optical device can be applied. For example, in addition to this, it can also be used for a fax machine with a display function, a finder of a digital camera, a portable TV, a DSP device, a PDA, an electronic notebook, an electric bulletin board, a display for advertisement announcement, and the like.

  By using the method for manufacturing a thin film transistor of the present invention, a high-quality poly-Si film can be formed with an extremely low amount of impurities. As a result, a TFT with extremely high characteristics can be manufactured. As a result, a multifunctional electro-optical device and electronic apparatus can be provided.

FIG. 6 is a process cross-sectional view illustrating a method for manufacturing a thin film transistor of the present invention. The diagram which showed transition of the crystallization rate with respect to the film thickness of the poly-si film | membrane which performed laser crystallization with a fixed laser irradiation energy density. Schematic of spectroscopic ellipsometry. Schematic of an optical interference type film thickness measuring apparatus. The figure which shows the semiconductor film formation chamber which equipped with the film thickness measuring apparatus. The figure which shows the light irradiation chamber which comprised the film thickness measuring apparatus. The figure which shows the conveyance chamber which comprised the film thickness measuring apparatus. The figure which shows typically the laser beam irradiation method at the time of laser crystallization. The figure which shows typically the laser beam irradiation method at the time of laser crystallization. FIG. 14 is a diagram illustrating an example of an electronic apparatus including the electro-optical device according to the invention. FIG. 14 is a diagram illustrating an example of an electronic apparatus including the electro-optical device according to the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Substrate 101 Base protective film 102 Semiconductor film 103 Film thickness measuring device 104 Laser light 105 Crystallized semiconductor layer 106 Plasma 107 Gate insulating film 108 Gate electrode 109 Source and drain region 110 Interlayer insulating film 111 Source and drain electrode 300 Light source 301 Polarization Plate 302 Light detection plate 303 Light receiving element 400 Light source 401 Light receiving element 500 Semiconductor film forming chamber 501 Film thickness measuring device 502 Shutter 503 Substrate 504 Stage 505 Shower plate 506 Transfer hand 600 Laser irradiation chamber 601 Film thickness measuring device 602 Shutter 603 Substrate 604 Stage 605 Laser irradiation device 606 Laser light 700 Transfer chamber 701 Film thickness measurement device 702 Substrate 703 Transfer hand 800 Substrate 801 Laser irradiation region 803 X direction 804 Y direction Direction 900 Substrate 901 Line beam 1000 Mobile phone 1001 Antenna 1002 Audio output unit 1003 Audio input unit 1004 Operation unit 1100 Video camera 1101 Image receiving unit 1102 Operation unit 10 Electro-optical device using TFTs manufactured using a semiconductor thin film according to the present invention

Claims (8)

  A first step of forming a semiconductor layer serving as a channel portion on the substrate; a second step of measuring the thickness of the semiconductor layer; a third step of transporting the substrate; and crystallization of the semiconductor layer by light irradiation. In the method of manufacturing a thin film transistor, the first step, the second step, the third step, and the fourth step are continuously performed without being exposed to the atmosphere. Method.   2. The method of manufacturing a thin film transistor according to claim 1, wherein the first step and the second step are performed in the same atmosphere.   2. The method of manufacturing a thin film transistor according to claim 1, wherein the second step and the third step are performed in the same atmosphere.   A first step of forming a semiconductor layer to be a channel portion on the substrate; a second step of transporting the substrate; a third step of measuring the thickness of the semiconductor layer; and crystallization of the semiconductor layer by light irradiation. In the method of manufacturing a thin film transistor, the first step, the second step, the third step, and the fourth step are continuously performed without being exposed to the atmosphere. Method.   5. The method of manufacturing a thin film transistor according to claim 4, wherein the third step and the fourth step are performed in the same atmosphere.   6. The method of manufacturing a thin film transistor according to claim 1, wherein the thickness of the semiconductor layer is measured by irradiating light perpendicular to the substrate. Production method.   An electro-optical device comprising: a thin film transistor manufactured by the method according to claim 1 as a driving element of a display pixel. An electronic apparatus comprising the electro-optical device according to claim 7.

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