JP2007220918A - Laser annealing method, thin-film semiconductor device, manufacturing method thereof, display, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser annealing method whereby the crystal grain-sizes of a polysilicon film can be made uniform over the whole of a substrate, a thin-film semiconductor device, a manufacturing method thereof, a display, and a manufacturing method thereof. <P>SOLUTION: The laser annealing method is so performed that a film material including an amorphous silicon film disposed on a substrate is irradiated by a linear beam shaped by using the laser beam emitted from a pulse-laser light source whose wavelength is not shorter than 350 nm and not longer than 800 nm. The semiconductor thin film crystallized by using this laser annealing method is so disposed on a substrate via an insulating film as to obtain a thin-film semiconductor device. The element comprising the semiconductor thin film crystallized by such method is so disposed on a displaying substrate as to obtain a display. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser annealing method, a thin film semiconductor device provided with a semiconductor thin film formed by using this method, a manufacturing method thereof, a display device using this semiconductor thin film, and a manufacturing method thereof.

  Organic EL displays (OLEDs) and liquid crystal displays (LCDs) using low-temperature polysilicon thin film transistors (LTPS TFTs) are attracting attention as high-definition, high-quality flat panel displays (FPDs). One of the key processes supporting the manufacture of this LTPS TFT is to form a laser beam generated from a pulsed laser light source into a linear beam into an amorphous silicon film (hereinafter also referred to as a-Si film) on a glass substrate. This is a laser annealing step in which the a-Si film is melted and crystallized by irradiation to form a polycrystalline silicon film (hereinafter also referred to as a poly-Si film). The crystal grain size of the poly-Si film to be formed varies depending on the intensity of the laser beam to be irradiated. Currently, excimer lasers (KrF (wavelength: 248 nm), XeCl (wavelength: 308 nm), etc.) that are UV light sources with a wavelength of 380 nm or less are used as light sources for laser annealing in FPD production lines using LTPS TFTs. ing.

  The excimer laser uses a halogen-based gas as an excitation gas for laser oscillation, but the purity of the excitation gas deteriorates rapidly, and routine exchanging and maintenance of the excitation gas is required. In addition, it is necessary to replace the laser oscillator tube and the optical parts due to the active gas plasma, resulting in a large dyne time and a large running cost. Furthermore, sudden fluctuations in the laser pulse occur due to fluctuations peculiar to the discharge phenomenon.

Solid-state lasers have attracted attention and researched as light sources that have the potential to solve the above-mentioned problems of excimer lasers. For solid-state lasers, high output and uniform linear beam were technical issues, but these problems were solved and the second harmonic (wavelength: 532 nm) of Q-switched Nd: YAG laser (hereinafter referred to as solid-state green laser) Recently, a production laser annealing apparatus equipped with a laser light source has been developed (see, for example, Non-Patent Documents 1 and 2).
IDW'04 Digest pp.615-618 (2004) SID'04 Digest pp.1088-1091 (2004)

  The solid green laser having a wavelength of 532 nm has a feature that the absorption coefficient of the a-Si film is smaller than that of the short wavelength ultraviolet excimer laser. In excimer laser annealing, incident laser light is attenuated by absorption and reflection by a laminated film having a normal film thickness formed on the substrate, and therefore hardly reaches the glass substrate. On the other hand, in the solid green laser, a part of incident light passes through the laminated film on the upper part of the substrate and reaches the substrate. If the laminated film on the top of the substrate has the same film configuration over the entire surface of the substrate (equivalent to the case of top gate type TFT fabrication), a small absorption coefficient will affect the formation of a poly-Si film with a uniform grain size do not do. However, in a configuration in which a patterned electrode film is formed on a substrate and a laminated film such as an insulating film and an a-Si film is formed on the electrode film (corresponding to the production of a bottom gate TFT), Thus, there may be a problem in the uniformity of the particle size of the formed poly-Si film. In addition, the reflected light of the incident laser light that has reached the electrode film is reabsorbed by the upper laminated film, and the absorption rate of the laser light is obtained by the laminated film above the electrode film and the laminated film on the glass substrate in the region without the electrode film. There may be differences. As a result, there may be a difference in the grain size of the poly-Si film formed between the laminated film on the electrode film and the laminated film on the glass substrate in the region without the electrode film. It becomes difficult to make uniform over the whole area.

  In addition, when fabricating either a bottom gate type TFT or a top gate type TFT, the absorption rate of incident laser light is changed to an excimer laser in the case of a solid green laser depending on the film thickness of the laminated film formed on the substrate. Compared to a large change. As a result, since the absorption rate of the laminated film is low, the laser light intensity required for crystallization may be larger than that of the excimer laser, and there is a problem that the utilization efficiency of the laser light may be deteriorated.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, making it possible to make the crystal grain size of the poly-Si film uniform over the entire substrate, and to make efficient use of laser light. An improved laser annealing method, a thin film semiconductor device provided with a semiconductor thin film formed using this method, a manufacturing method thereof, a display device using this semiconductor thin film, and a manufacturing method thereof is there.

  The laser annealing method of the present invention is characterized in that a laser beam generated from a pulsed laser light source having a wavelength of 350 nm or more and 800 nm or less is formed into a linear beam and irradiated onto a film material on the substrate.

  The film material on the substrate is an amorphous silicon film alone or a multilayer film in which an amorphous silicon film and an insulating film are stacked. The insulating film includes a silicon oxide film and a silicon nitride film. It is preferably at least one film selected from physical films.

  The film material on the substrate is preferably formed on a patterned electrode film.

  Further, according to the laser annealing method, the film thickness of the amorphous silicon film used as the film material on the substrate is controlled so that the light absorption rate of the irradiation laser light is increased, and the substrate is obtained with a smaller irradiation laser light intensity. A polycrystalline silicon film having a uniform grain size is formed in the plane.

  Furthermore, according to the laser annealing method, the light absorption rate of the irradiation laser light is controlled by controlling the film thickness of each layer of the multilayer film used as the film material on the substrate, and the uniform large particle diameter is obtained within the substrate surface. A polycrystalline silicon film is formed.

  Furthermore, according to the laser annealing method, the film thickness of each layer of the multilayer film used as the film material on the substrate is controlled so that the light absorption rate of the irradiation laser light is increased, and the substrate can be formed with a smaller irradiation laser light intensity. A polycrystalline silicon film having a uniform grain size is formed in the plane.

  The pulsed laser light source used in this laser annealing method is the second or third harmonic of a Q-switched Nd: YAG laser, the second or third harmonic of an Nd: glass laser, and the second of an Nd: YLF laser. Harmonic or third harmonic, Yb: YAG or Yb: second harmonic or third harmonic of Yb ion-doped solid-state laser of glass, or fundamental or second harmonic of Ti: sapphire laser The second harmonic (wavelength: 532 nm) or the third harmonic (wavelength: 355 nm) of a Q-switched Nd: YAG laser is more preferable.

  The thin film semiconductor device of the present invention is a thin film semiconductor device in which a semiconductor thin film is provided via an insulating film on a substrate on which a light absorption layer patterned into a wiring shape including a gate electrode is formed. The film is characterized by being crystallized by irradiating a linear beam obtained by shaping a laser beam generated from a pulse laser light source having a wavelength of 350 nm or more and 800 nm or less and laser annealing. In this case, the pulse laser light source to be used is as described above.

  In the semiconductor device, the insulating film is preferably at least one film selected from a silicon oxide film and a silicon nitride film, and the semiconductor thin film is preferably an amorphous silicon film.

  The manufacturing method of a thin film semiconductor device of the present invention forms a film material for a thin film semiconductor device including a semiconductor thin film on a substrate on which a light absorption layer patterned into a wiring shape including a gate electrode is formed. On the other hand, the semiconductor thin film is laser-annealed by irradiating a linear beam obtained by shaping a laser beam generated from a pulse laser light source having a wavelength of 350 nm or more and 800 nm or less, and is crystallized. The pulse laser light source used in this case is as described above. The film material is an amorphous silicon film alone or a multilayer film in which an amorphous silicon film and a film that is at least one insulating film selected from a silicon oxide film and a silicon nitride film are stacked. In addition, a multilayer film laminated on a light absorption layer which is a patterned electrode film is preferable.

  In the manufacturing method of the thin film semiconductor device of the present invention, the light absorption rate of the irradiation laser light is controlled by controlling the film thickness of each layer of the multilayer film used as the film material, and the uniform large particle diameter is obtained within the substrate surface. A polycrystalline silicon film is preferably formed. In addition, the thickness of each layer of the multilayer film used as the film material is controlled so that the light absorption rate of the irradiation laser light is increased, and polycrystalline silicon having a uniform particle diameter within the substrate surface with a smaller irradiation laser light intensity. A film can also be formed.

  The display device of the present invention is a display device in which a thin film semiconductor element is provided on a display substrate, and the thin film semiconductor element is insulated on the substrate on which the light absorption layer patterned in a wiring shape including the gate electrode is formed. A semiconductor thin film is provided via a film, and the semiconductor thin film is subjected to laser annealing by irradiating a linear beam formed by a laser beam generated from a pulse laser light source having a wavelength of 350 nm or more and 800 nm or less. It is characterized by being a crystallized film. The pulse laser light source in this case is as described above. The insulating film is preferably at least one film selected from a silicon oxide film and a silicon nitride film, and the semiconductor thin film is preferably an amorphous silicon film.

  The display device includes an organic EL element connected to a thin film semiconductor element on a display substrate, and a pixel electrode for driving a liquid crystal connected to the thin film semiconductor element on the display substrate. Is preferred.

  The display device manufacturing method of the present invention is a display device manufacturing method in which a thin film semiconductor element is provided on a display substrate, and is insulated on the substrate on which the light absorption layer patterned into a wiring shape including a gate electrode is formed. A semiconductor thin film is formed through a film to form a thin film semiconductor element, and laser annealing is performed by irradiating the semiconductor thin film with a linear beam formed by a pulsed laser light source having a wavelength of 350 nm or more and 800 nm or less. And crystallizing. The pulse laser light source used in this case is as described above. The insulating film is at least one film selected from a silicon oxide film and a silicon nitride film, and the semiconductor thin film is preferably an amorphous silicon film.

  In the display device manufacturing method, an organic EL element is formed on a display substrate by being connected to a thin film semiconductor element, and a liquid crystal driving pixel electrode is formed on the display substrate by being connected to the thin film semiconductor element. It is preferable.

  According to the laser annealing method of the present invention, even when a laminated film configuration composed of different layers is mixed on the substrate, for example, when producing a bottom gate type TFT, the particle size of the substrate is substantially uniform, In addition, the poly-Si film having a large grain size can be formed, and an optimum crystal grain size can be obtained by adopting a film thickness configuration that increases the absorption rate of incident laser light by the laminated film. There is an effect that it is possible to reduce the intensity of the laser beam necessary to have it.

  In addition, if a semiconductor thin film is formed using the laser annealing method of the present invention, a semiconductor thin film having a large particle size with a uniform particle size distribution can be obtained. There is an effect that an excellent thin film semiconductor device can be provided.

  Furthermore, according to the display device provided with the thin film semiconductor element using the semiconductor thin film obtained by using the laser annealing method of the present invention, the display device having the thin film semiconductor element of the bottom gate type structure, for example, In this case, there is an effect that the thin film semiconductor element in this display device has good TFT characteristics.

Normally, when fabricating a bottom gate type TFT, an SiN _x film or SiO _x film is formed as an insulating film on a glass substrate having a patterned gate electrode film, and a-Si is formed on the insulating film. A film is formed to form a laminated film.

  In the present invention, the film thickness of these laminated films is controlled so that the laminated film on the upper part of the wiring including the gate electrode (this wiring is simply referred to as a gate electrode film hereinafter) and the gate electrode film are not patterned. The absorption rate of incident laser light is made to be substantially the same for the laminated film on the glass substrate. By making the absorption rate substantially the same, the laser energy absorbed by each laminated film is almost the same between the upper part of the gate electrode film and the upper part of the glass substrate without the gate electrode film. The particle size can be made substantially the same between the upper part of the electrode film and the upper part of the glass substrate without the electrode film.

In addition to the bottom gate type TFT, the top gate type TFT can be manufactured by controlling the film thickness of the SiN _x film, the SiO _x film, and the a-Si film laminated on the glass substrate. The film thickness can be increased so that the absorption rate of incident laser light by the film is increased, and the laser light intensity necessary for obtaining an optimum crystal grain size can be reduced.

  Hereinafter, an embodiment of the laser annealing method of the present invention will be described. First, an example of a laminated film configuration used at the time of laser annealing when manufacturing a bottom gate type TFT will be described.

  A gate electrode film is formed on a substrate made of glass, transparent plastic, or the like. That is, a metal film made of a metal selected from Mo, Ta, W, Cr, Al, or the like, or an alloy containing at least one of these metals is formed on the substrate by a known sputtering method. A photoresist is applied on the metal film and then patterned, and etching is performed using the obtained resist pattern as a mask to form a gate electrode film having a predetermined pattern shape. The electrode film may be a known multilayer film.

Next, an insulating layer is formed so as to cover the gate electrode film. Although there is no restriction | limiting in particular as this insulating layer, For example, it is preferable to consist of any one or both of an oxide film and a nitride film. As this insulating film, for example, at least one film selected from, for example, a silicon nitride film (SiN _x film) and a silicon oxide film (SiO _x film), preferably a two-layer structure including these two films is used. Can do.

  This silicon nitride film is formed with a film thickness of 50 to 200 nm under known process conditions using, for example, silane gas and ammonia gas according to the plasma CVD method. In addition, it may be formed using a normal pressure CVD method, a low pressure CVD method, a sputtering method, a vapor deposition method, or the like. In addition, the silicon oxide film has a thickness of 50 to 300 nm under a known process condition according to the above-described plasma CVD method using a silane gas and an oxygen atom-containing gas (for example, oxygen gas or nitrogen oxide gas). Form.

  Thereafter, an a-Si film is formed on the insulating film with a film thickness of 40 to 100 nm under a known process condition using a silane gas according to, for example, a plasma CVD method.

For the a-Si / SiO _x / SiN _x / gate electrode film / glass substrate laminated film configuration thus obtained, a laminated film on the gate electrode film and a laminated film on the substrate without the gate electrode film being patterned In order to reduce the difference in the absorption rate of incident solid green laser light (eg about 5%), laser annealing is performed by irradiating a shaped linear laser beam, and a-Si is crystallized to poly-Si. The target thin film is formed.

  Next, laser light used in the present invention will be described. Since the absorption rate of the laser beam to be irradiated is determined by the laminated film configuration, the same effect can be obtained for all laser beams having a wavelength of 350 nm to 800 nm having the same order of absorption rate. That is, since the laser energy absorbed by each laminated film can be made substantially the same between the upper part of the gate electrode film and the upper part of the substrate without the gate electrode film, the crystal grain size of the formed poly-Si film can be set to the gate electrode. The upper part of the film and the upper part of the substrate without the gate electrode film can be made substantially the same. Therefore, the second harmonic of the Nd: YAG laser, the third harmonic of the Nd: YAG laser, the second or third harmonic of the Nd: glass laser, the second or third harmonic of the Nd: YLF laser, Yb: Perform laser annealing to achieve the same effect using the second or third harmonic of a Yb ion-doped solid-state laser such as YAG or Yb: glass, or the fundamental or second harmonic of a Ti: Sapphire laser. Can do. Among these, the second harmonic (wavelength: 532 nm) of the Nd: YAG laser has the merit that the productivity of the laser annealing treatment is good because the laser oscillation efficiency is high and a high output is obtained. Most convenient for use in the invention.

According to the present invention, as shown in the following examples, in the laminated film structure as described above, a region on the substrate having a larger laser light absorption rate has crystals formed at a lower energy density, and When the absorptances of the laminated films of the upper part of the gate electrode film and the upper part of the substrate without the gate electrode film are substantially equal, the way of changing the poly-Si average crystal grain size depending on the energy density is substantially equal. Therefore, even when different laminated film configurations are mixed on the substrate as in the case of manufacturing a bottom gate type TFT, the film thickness of the laminated film is controlled so that the absorption rate of the irradiation laser light is almost the same. As a result, it can be seen that a poly-Si film having a large uniform particle diameter can be formed on the substrate surface. In this case, by controlling the a-Si film thickness, it is possible to form a poly-Si film having a substantially uniform large particle size within the substrate surface, and also to include other constituent films of the laminated film. The same effect can be obtained even if the thickness is controlled. That is, as shown in the following examples, by controlling the film thickness of the SiO _x film and / or the SiN _x film, the absorptance of each laminated film of the upper part of the gate electrode film and the upper part of the substrate without the gate electrode film is adjusted. Can be almost equal.

  According to the present invention, when the a-Si film thickness has a small difference in the absorptivity of the laminated film between the upper part of the gate electrode film and the upper part of the glass substrate without the gate electrode film, the poly- The difference in crystal grain size of the Si film is small, and in the case of an a-Si film thickness with a large difference in absorption rate, the difference in crystal grain size is estimated to be large. In this case, if the difference in absorptance is within 5%, the difference in the average crystal grain size of the poly-Si film is within 0.1 μm, and the particle size is almost uniform. %, It is possible to obtain a Poly-Si film having the same particle size. In order to obtain such a Poly-Si film having the same particle size, the a-Si film thickness is about 20-28 nm, about 65-86 nm, and about 116-148 nm, as shown in the following examples. It is preferable that it is the range of these. Within this film thickness range, it is possible to form a poly-Si film having a substantially uniform grain size within the substrate surface and over the entire film thickness. When the a-Si film thickness is less than 20 nm, when it exceeds 28 nm and less than 65 nm, when it exceeds 86 nm and less than 116 nm, it is difficult to form a-Si with a uniform film thickness over the entire surface of the substrate, Since the film thickness uniformity deteriorates, it becomes difficult to form a poly-Si film having a substantially uniform particle diameter within the substrate surface by laser annealing. Also, if the a-Si film thickness exceeds 148 nm, the difference in the amount of laser light absorption due to the film depth increases, making it difficult to form a uniform poly-Si film over the entire film thickness by laser annealing. .

  Furthermore, according to the present invention, it is possible to reduce the laser light intensity necessary for obtaining an optimum crystal grain size by adopting a film thickness configuration in which the absorption rate of incident laser light by the laminated film is increased. .

  The laser annealing apparatus used in the laser annealing method of the present invention is a pulse laser light source having a wavelength of 350 nm or more and 800 nm or less, and a linear beam forming device for forming a laser beam generated from the pulse laser light source into a linear beam. And an optical system. As described above, this laser annealing apparatus, for example, forms a poly-Si film by irradiating a shaped linear beam onto an a-Si film, or forms an insulating film having a predetermined film thickness with a gate electrode film. It can be used when manufacturing a crystallized semiconductor thin film by irradiating a shaped linear beam on a multilayer film material having a film and a semiconductor thin film having a predetermined film thickness and laser annealing. The pulse laser light source in this case is not particularly limited, and a sufficiently satisfactory annealing process can be performed with the above light source.

  Hereinafter, a thin film semiconductor device having a bottom gate poly-Si thin film transistor (TFT) according to an embodiment of the present invention and a manufacturing method thereof will be described. This thin film semiconductor device can be manufactured according to known process conditions except for the laser annealing treatment step of the present invention.

  First, as described above, a gate electrode film is formed on a substrate made of glass or the like. At this time, a metal film made of the above metal or alloy is formed with a predetermined thickness by a sputtering method, and then a resist pattern is formed by a photolithographic technique, and the above metal film is formed by dry etching or wet etching using this as a mask. Is processed into a predetermined shape to form a patterned gate electrode film. In order to reduce the electric resistance of the gate electrode film, a metal film having a multilayer structure obtained by first forming a low resistance metal film on the substrate and laminating the metal film thereon may be formed. .

Next, an insulating film is formed so as to cover the gate electrode film. For example, the gate insulating film may be formed in a two-layer structure including a silicon nitride film and a silicon oxide film formed thereon. First, using a silane gas (SiH ₄ gas) and an ammonia gas (NH ₃ gas), a silicon nitride film is formed to a predetermined thickness (for example, about 50 to 200 nm) at a substrate temperature of about 400 ° C. by plasma CVD. To do. In this case, atmospheric pressure CVD, reduced pressure chemical vapor deposition, sputtering, or vapor deposition may be used. Thereafter, a silicon oxide film is formed with a predetermined film thickness (for example, about 50 to 300 nm) using silane gas and nitrogen oxide gas (N ₂ O gas).

  On the insulating film, a predetermined semiconductor thin film made of a-Si or poly-Si having a small particle size (for example, about 0.1 μm or less) is used, for example, by a plasma CVD method under known conditions, using only silane gas. With a thickness of (for example, about 40 to 100 nm).

  For the semiconductor thin film having the laminated film structure of a-Si / SiOx / SiNx / gate electrode film / glass substrate thus obtained, the laminated film on the upper part of the gate electrode film and the laminated film on the upper part of the substrate without being patterned. In order to reduce the difference in the absorption rate of the incident solid green laser light from the film (for example, about 5%), laser annealing is performed by irradiating the linear laser beam formed as described above. Crystallize into poly-Si to form the desired thin film. At this time, the semiconductor thin film is heated by the laser light irradiation, and the wavelength of the laser light is selected so that the gate electrode film is heated to a temperature equal to or higher than that of the semiconductor thin film. The temperature should be such that there is almost no heat conduction to the electrode film. As the wavelength of such laser light, any wavelength can be used as long as it can be obtained from the above-described light source.

  After the semiconductor thin film is crystallized as described above, a stopper film is patterned on the crystallized semiconductor thin film using an insulating material by a plasma CVD method or the like under known process conditions. By this stopper film, the semiconductor thin film portion located immediately below is protected as a channel portion.

Subsequently, impurities (for example, P ⁺ ions) are implanted into the semiconductor thin film by ion implantation using the stopper film as a mask to form a low concentration offset region. The dose amount at this time may be the same as the normal impurity implantation amount. Further, after patterning the photoresist so as to cover the stopper film and the offset regions on both sides thereof, impurities (for example, P ⁺ ions) are again implanted at a high concentration using this as a mask, and N is formed on both sides of the offset region. Form the source and drain of the mold. For such impurity implantation, for example, ion doping can be used.

  In order to activate the impurities implanted into the semiconductor thin film as described above, known activation annealing using rapid thermal annealing is performed. As a result, a bottom-gate poly-Si TFT can be obtained.

  Thereafter, the semiconductor thin film is etched to separate each poly-Si TFT portion.

  Next, a silicon oxide film and a silicon nitride film are formed with a predetermined thickness by plasma CVD, and an interlayer insulating film having a two-layer structure is obtained. Thereafter, a contact hole or the like is opened in the interlayer insulating film, Al or Ti or the like is sputtered to a predetermined thickness with a single layer or a multilayer layer, and then patterned into a predetermined shape to form a wiring electrode. Further, after applying a photosensitive flattening layer made of an acrylic resin or the like, a contact hole is opened by photolithography. A transparent conductive film made of, for example, ITO is sputtered on the planarizing layer, and then the transparent conductive film is patterned into a predetermined shape to be processed into pixel electrodes connected to the source / drain through contact holes. To do.

  Thus, a circuit board for a display device having a bottom-gate type poly-Si TFT on a substrate and having a pixel electrode connected thereto is obtained as a thin film semiconductor device.

  Next, an embodiment of an active matrix display device using a thin film semiconductor device (circuit board) manufactured according to the manufacturing method of the above-described embodiment and a manufacturing method thereof will be described. This display device can be manufactured according to known process conditions except for the laser annealing treatment step of the present invention.

  The display device of the present invention is crystallized on a display substrate by irradiating a linear beam obtained by shaping a laser beam generated from a pulse laser light source having a wavelength of 350 nm to 800 nm as described above, and laser annealing. A thin film semiconductor element provided with a semiconductor thin film is provided, and this semiconductor thin film is provided on a substrate on which a gate electrode film is formed via an insulating film. The insulating film is at least one film selected from a silicon oxide film and a silicon nitride film, and the semiconductor thin film is an a-Si film. An organic EL element connected to the thin film semiconductor element is provided on the display substrate of the display device, and a pixel electrode for driving a liquid crystal connected to the thin film semiconductor element is provided on the display substrate. . Such a display device is connected to a thin film semiconductor element on a display substrate to form a device using an organic EL element or liquid crystal, and is connected to the thin film semiconductor element on the display substrate for an organic EL element. And a pixel electrode for driving a liquid crystal.

  Hereinafter, the display device of the present invention will be described in detail by taking a liquid crystal display device as an example. The manufacturing method of the display device of the present invention is not particularly limited as long as the laser annealing method of the present invention can be used. This display device can be manufactured according to known process conditions except for the laser annealing treatment step of the present invention.

  For example, as the display device of the present invention, a liquid crystal display device having a panel structure including a pair of insulating substrates and a known liquid crystal material held between the insulating substrates can be given. . A pixel array portion and a drive circuit portion are integrated on the lower insulating substrate. This drive circuit section is divided into a vertical scanner and a horizontal scanner. Further, a terminal for external connection is formed in the peripheral portion of the upper surface of the lower insulating substrate, and this terminal is connected to the vertical scanner and the horizontal scanner via wiring. A gate electrode film and a signal wiring film are formed in the pixel array portion. A pixel electrode and a TFT for driving the pixel electrode are formed at the intersection between the gate electrode film and the signal wiring film.

  The TFT gate electrode is connected to the corresponding gate electrode film, the drain is connected to the corresponding pixel electrode, and the source is connected to the corresponding signal wiring film. The gate electrode film is connected to the vertical scanner, and the signal wiring film is connected to the horizontal scanner.

  The TFT included in the thin film transistor and the vertical scanner and the horizontal scanner for switching driving the pixel electrode is a bottom-gate type poly-Si TFT manufactured according to the method of the present invention as described above. The circuit board which is the lower insulating substrate on which the above circuit is formed becomes a thin film semiconductor device.

  In the display device having the above-described configuration, since the crystallinity and grain size of the channel portion of the thin film transistor are improved, the same characteristics can be achieved with respect to the current driving capability and the like with a smaller TFT. Furthermore, since a display device provided with a thin film semiconductor element provided with a semiconductor thin film having a large particle size with a uniform particle size distribution obtained by using the laser annealing method of the present invention can be provided, particularly a bottom gate type structure is provided. In the case of a display device having a thin film semiconductor element, the thin film semiconductor element in the display device has good TFT characteristics.

  The display device may be a display device using a self-luminous element such as an organic EL element in addition to the liquid crystal display device described above, for example, an active matrix display using an organic EL element. If it is a device, a lower insulating substrate having the same configuration as that of the liquid crystal display device may be used. Then, the pixel electrode is used as an anode or a cathode, and a plurality of organic layers including an organic light emitting layer are stacked on the pixel electrode. Further, a cathode or an anode is stacked on these organic layers, whereby the anode and the cathode Each light-emitting element having an organic layer interposed therebetween can be formed. Thus, an active matrix display device in which each light emitting element is connected to the TFT is configured, and the same effect as the liquid crystal display device can be obtained.

  In the following, examples of the present invention will be described, in particular, specific examples of laser annealing methods.

  FIG. 1 schematically shows an example of a laminated film configuration used at the time of laser annealing when a bottom gate type TFT is manufactured. As shown in FIG. 1, a gate electrode film 2 was formed on a glass substrate 1 under the following process conditions. The process conditions are Ar flow rate: 100 sccm, pressure: 0.3 Pa, substrate temperature: 120 ° C., and sputtering power: 15 kW.

Next, gate insulating films 3 and 4 were formed under the following process conditions so as to cover the gate electrode film 2. In this embodiment, the gate insulating film 3 is a nitride film made of a SiN _x film, and the gate insulating film 4 is an oxide film made of SiO _x , each having a two-layer structure formed with a thickness of 50 nm. For SiN _x films, these process conditions are: SiH ₄ gas flow rate: 400 sccm, N ₂ gas flow rate: 4 slm (standard liter / min), NH ₃ gas flow rate: 6 slm, pressure: 300 Pa, substrate temperature: 400 ° C., and RF power: 4 kW, and for SiO _x film, SiH ₄ gas flow rate: 400 sccm, Ar gas flow rate: 8 slm, N ₂ O gas flow rate: 7 slm, pressure: 200 Pa, substrate temperature: 400 ° C., and RF power: 1.4kW.

Thereafter, an a-Si film 5 having a thickness of 20 to 150 nm was formed on the gate insulating film 4 using SiH ₄ gas.

The a-Si / SiO _x (50 nm) / SiN _x (50 nm) / gate electrode film / glass substrate laminated film structure thus obtained is used for solid green laser light (second harmonic of a Q-switched Nd: YAG laser ( The incident solid-state green laser light in the laminated film on the gate electrode film and the laminated film on the glass substrate without the gate electrode film when the a-Si film thickness is changed by irradiating the wavelength: 532 nm)) The results are shown in FIG.

  As is apparent from FIG. 2, it can be seen that the absorptivity changes greatly depending on the a-Si film thickness between the laminated film on the gate electrode film and the laminated film on the glass substrate without the gate electrode film. . In the case of a-Si film thickness where the difference in the absorption rate of each laminated film is small between the upper part of the gate electrode film and the glass substrate without the gate electrode film, the crystal grain size of the poly-Si film formed by laser annealing On the other hand, in the case of an a-Si film thickness where the difference in absorption is large, the difference in crystal grain size is estimated to be large. In this case, if the difference in absorptivity is within 5%, the difference in the average crystal grain size of the poly-Si film is within 0.1 μm and the particle size is almost uniform. If it is within the range, a Poly-Si film having substantially the same particle diameter can be obtained.

  Thus, according to the experiments of the present inventors, in order to obtain a Poly-Si film having the same grain size in the above laminated film configuration, as is apparent from FIG. 2, the a-Si film thickness is 20 to 28 nm. In the range of about 65 to 86 nm and 116 to 148 nm, a poly-Si film having a substantially uniform grain size could be formed in the substrate surface and over the entire film thickness. When the a-Si film thickness is less than 20 nm, when it exceeds 28 nm and less than 65 nm, when it exceeds 86 nm and less than 116 nm, it is difficult to form a-Si with a uniform film thickness over the entire surface of the substrate, Due to the poor film thickness uniformity, it was difficult to form a poly-Si film having a substantially uniform grain size within the substrate surface by laser annealing. Further, when the a-Si film thickness exceeds 148 nm, the difference in the amount of laser light absorption depending on the film depth becomes large, and it is difficult to form a uniform poly-Si film over the entire film thickness by laser annealing.

In accordance with the procedure described in Example 1, both a SiN _x film and a SiO _x film are laminated in this order on a patterned electrode film in a thickness of 50 nm, and an a-Si film is formed thereon with a thickness of 50 nm. Laser annealing of the substrate formed with two kinds of film thicknesses of 70 nm was performed by changing the energy density (mJ / cm ² ) of the irradiation laser beam. The substrate after laser annealing was Secco etched and then subjected to SEM measurement, and the average crystal grain size (μm) of the formed poly-Si was calculated. FIGS. 3 and 4 show the relationship between the energy density and the average crystal grain size obtained when the a-Si film thickness is 50 nm and 70 nm, respectively.

  As is clear from FIG. 3, when the a-Si film thickness is 50 nm (see FIG. 2) where the absorption ratios of the stacked films of the upper part of the gate electrode film and the upper part of the glass substrate without the gate electrode film are greatly different, The way of changing the poly-Si average grain size depending on the energy density is greatly different. That is, it can be seen that a poly-Si crystal is formed at a lower energy density in the laminated film on the gate electrode film having a larger laser light absorption rate.

  On the other hand, as can be seen from FIG. 4, the a-Si film thickness at which the absorptivity of the laminated films of the upper part of the gate electrode film and the upper part of the glass substrate without the gate electrode film is almost equal is 70 nm (see FIG. 2). In the case of), the poly-Si average crystal grain size is almost equal in how it changes depending on the energy density. This makes it possible to control the film thickness of the laminated film so that the absorptivity of the irradiated laser beam is almost the same even when different laminated film configurations are mixed on the glass substrate, as in the case of manufacturing a bottom gate type TFT. By doing so, it can be seen that a poly-Si film having a substantially uniform large grain size can be formed in the substrate surface.

  In the embodiment described above, it was shown that a poly-Si film having a substantially uniform large grain size can be formed in the substrate surface by controlling the a-Si film thickness. As shown, the same effect can be obtained by controlling other constituent film thicknesses of the laminated film.

According to the procedure described in Example 1, when the SiO _x film thickness is changed as the laminated film configuration of a-Si (50 nm) / SiO _x / SiN _x (50 nm) / gate electrode film / glass substrate, and As a laminated film configuration of a-Si (50 nm) / SiO _x (50 nm) / SiN _x / gate electrode film / glass substrate, the absorption rate of incident laser light in each case when the SiN _x film thickness is changed The results are shown in FIGS.

From these figures, by controlling the film thickness of the SiO _x film or SiN _x film, it is possible to make the absorptivity of each laminated film of the upper part of the gate electrode film and the upper part of the glass substrate without the gate electrode film substantially equal. I understand. That is, when the SiO _x film thickness is about 108 to 141 nm, and when the SiN _x film thickness is about 90 to 115 nm, the absorptivity of the laminated film is within 5%, and the same uniform particle size is obtained. It can be seen that a poly-Si film can be formed.

As is apparent from FIG. 2, the solid green laser light absorptance for the gate electrode film in the laminated film structure of a-Si / SiO _x (50 nm) / SiN _x (50 nm) / gate electrode film / glass substrate is In each of the upper part and the upper part of the glass substrate without the gate electrode film, it changes depending on the a-Si film thickness, the a-Si film thickness is large in the vicinity of 40 to 65 nm and 100 to 120 nm, and the film thickness is out of this range. Get smaller.

Therefore, in this example, both the SiN _x film and the SiO _x film are laminated in this order on the glass substrate in a thickness of 50 nm, and the a-Si film thickness is 40 nm, 50 nm, 60 nm, and 70 nm thereon. Laser annealing was performed on the substrates formed with the four types of film thicknesses while changing the energy density of the irradiation laser light. SEM measurement is performed after Secco etching of the substrate after laser annealing, the average crystal grain size at each energy density is calculated, and the average grain size of 0.5 μm and 1.0 μm for each thickness of the a-Si film The energy density at which a crystal with a diameter was obtained was calculated. The obtained results are shown in FIG.

  As is clear from FIG. 7, the energy density required for crystal formation tends to be different from the laser light absorption rate of FIG. 2, and the energy density is the lowest when the a-Si film thickness is around 60 nm. Even if it is made thinner or thicker, the energy density required for crystal formation becomes higher. From this, it is understood that the laser beam intensity required for obtaining the optimum crystal grain size can be reduced by adopting a film thickness configuration in which the absorption rate of the incident laser beam by the laminated film is increased.

In Examples 1 to 4, the case where the second harmonic (wavelength: 532 nm) of the Nd: YAG laser is used has been described. The second harmonic of the Nd: YAG laser has a merit that the productivity of the laser annealing process is good because the laser oscillation efficiency is high and a high output is obtained. According to the gist of the present invention, the absorptivity of the laser beam to be irradiated is determined by the laminated film configuration of a-Si / SiO _x / SiN _x / gate electrode film / glass substrate. If the laser beam has a wavelength up to 800 nm, the same effect as in the case of 532 nm can be obtained.

Therefore, the third harmonic of an Nd: YAG laser having a wavelength of 350 nm to 800 nm, the second or third harmonic of an Nd: glass laser, the second or third harmonic of an Nd: YLF laser, Yb: YAG or Yb : Using the second or third harmonic of a Yb ion-doped solid laser such as glass or the fundamental or second harmonic of a Ti: Sapphire laser, a-Si / SiO _x By performing laser annealing on the laminated film structure of / SiN _x / gate electrode film / glass substrate, the laser energy absorbed by each laminated film at the upper part of the gate electrode film and the upper part of the glass substrate without the gate electrode film is reduced. The crystal grain size of the formed poly-Si film can be made substantially the same between the upper part of the gate electrode film and the upper part of the glass substrate without the gate electrode film.

  As described above, according to the laser annealing method of the present invention, even when different laminated film configurations are mixed on the substrate, particularly when a bottom gate type TFT is manufactured, a large size that is almost uniform within the substrate surface. It is possible to form a poly-Si film with a grain size, and the laser beam necessary to obtain the optimum crystal grain size by adopting a film thickness configuration that increases the absorption rate of incident laser light by the laminated film It is also possible to reduce the strength.

  In addition, if a semiconductor thin film is formed using the laser annealing method of the present invention, a semiconductor thin film having a large particle size with a uniform particle size distribution can be obtained. An excellent thin film semiconductor device can be provided.

  Further, according to the display device provided with the thin film semiconductor element using the semiconductor thin film obtained by utilizing the laser annealing method of the present invention, particularly in the case of the display device having the thin film semiconductor element of the bottom gate type structure, A thin film semiconductor element in a display device has good TFT characteristics.

  As described above, according to the present invention, a poly-Si film having excellent crystallinity and uniformity can be provided, and a TFT using this film can be realized. Therefore, the present invention uses this TFT. The present invention is applicable to the field of flat panel display devices such as organic EL displays and liquid crystal displays.

Sectional drawing which shows typically the laminated film structure at the time of laser annealing at the time of producing bottom gate type TFT. The graph which shows the change of a solid green laser absorptivity when a-Si film thickness is changed in the laminated film structure of a-Si / SiO _x (50 nm) / SiN _x (50 nm) / gate electrode film / glass substrate. In the laminated film configuration of a-Si (50 nm) / SiO _x (50 nm) / SiN _x (50 nm) / gate electrode film / glass substrate, the irradiation laser light energy density and the poly-Si average crystal grain size during laser annealing The graph which shows the relationship. In the laminated film configuration of a-Si (70 nm) / SiO _x (50 nm) / SiN _x (50 nm) / gate electrode film / glass substrate, the irradiation laser beam energy density and poly-Si average crystal grain size when laser annealing is performed The graph which shows the relationship. In a-Si (50nm) / SiO x / SiN x (50nm) / gate electrode film / laminate film structure of the glass substrate, the graph showing the change of the solid-state green laser absorptivity when changing the SiO _x film thickness. The graph which shows the change of a solid green laser absorptivity when SiNx film thickness is changed in the laminated film structure of a-Si (50 nm) / SiO _x (50 nm) / SiN _x / gate electrode film / glass substrate. In the laminated film configuration of a-Si (40-70 nm) / SiO _x (50 nm) / SiN _x (50 nm) / gate electrode film / glass substrate, crystals with an average grain size of 0.5 μm and 1.0 μm when laser annealed The graph which shows the relationship between the energy density obtained and a-Si film thickness.

Explanation of symbols

1 Glass substrate 2 Gate electrode film 3 SiN _x film 4 SiO _x film 5 a-Si film

Claims (27)

A laser annealing method characterized by forming a laser beam generated from a pulse laser light source having a wavelength of 350 nm or more and 800 nm or less into a linear beam and irradiating the film material on the substrate. 2. The laser annealing method according to claim 1, wherein the film material on the substrate is an amorphous silicon film alone or a multilayer film in which an amorphous silicon film and an insulating film are laminated. 3. The laser annealing method according to claim 2, wherein the insulating film is at least one film selected from a silicon oxide film and a silicon nitride film. The laser annealing method according to claim 1, wherein the film material on the substrate is formed on a patterned electrode film. The film thickness of the amorphous silicon film used as the film material on the substrate is controlled so that the light absorptance of the irradiation laser beam is increased, and the polycrystalline particle having a uniform grain size within the substrate surface with a smaller irradiation laser beam intensity. The laser annealing method according to claim 2, wherein a silicon film is formed. By controlling the film thickness of each layer of the multilayer film used as the film material on the substrate, the light absorptance of the irradiation laser beam is controlled, and a polycrystalline silicon film having a uniform large grain size is formed on the substrate surface. The laser annealing method according to any one of claims 2 to 4, wherein The thickness of each layer of the multilayer film used as the film material on the substrate is controlled so that the light absorptance of the irradiation laser light is increased, and the polycrystalline silicon has a uniform particle size within the substrate surface with a smaller irradiation laser light intensity. The laser annealing method according to claim 2, wherein a film is formed. The pulse laser source is the second or third harmonic of a Q-switched Nd: YAG laser, the second or third harmonic of an Nd: glass laser, or the second or third harmonic of an Nd: YLF laser. A harmonic, a second harmonic or a third harmonic of a Yb: YAG or Yb: glass Yb ion-doped solid-state laser, or a fundamental wave or a second harmonic of a Ti: sapphire laser. The laser annealing method according to any one of 1 to 7. In a thin film semiconductor device in which a semiconductor thin film is provided via an insulating film on a substrate on which a light absorption layer patterned into a wiring shape including a gate electrode is formed, the semiconductor thin film has a pulse having a wavelength of 350 nm or more and 800 nm or less A thin film semiconductor device characterized by being a film crystallized by irradiating a linear beam formed by a laser beam generated from a laser light source and laser annealing. 10. The thin film semiconductor according to claim 9, wherein the insulating film is at least one film selected from a silicon oxide film and a silicon nitride film, and the semiconductor thin film is an amorphous silicon film. apparatus. The pulse laser source is the second or third harmonic of a Q-switched Nd: YAG laser, the second or third harmonic of an Nd: glass laser, or the second or third harmonic of an Nd: YLF laser. A harmonic, a second harmonic or a third harmonic of a Yb: YAG or Yb: glass Yb ion-doped solid-state laser, or a fundamental wave or a second harmonic of a Ti: sapphire laser. The thin film semiconductor device according to 9 or 10. A film material for a thin film semiconductor device including a semiconductor thin film is formed on a substrate on which a light absorption layer patterned into a wiring shape including a gate electrode is formed, and the wavelength of the film material is 350 nm to 800 nm. A method of manufacturing a thin film semiconductor device, wherein a semiconductor thin film is laser-annealed by irradiating a linear beam formed from a laser beam generated from a pulsed laser light source and crystallized. The film material is an amorphous silicon film alone or a multilayer film in which an amorphous silicon film and a film that is at least one insulating film selected from a silicon oxide film and a silicon nitride film are laminated. The method of manufacturing a thin film semiconductor device according to claim 12. 14. The method of manufacturing a thin film semiconductor device according to claim 12, wherein the film material is a multilayer film laminated on a light absorption layer which is a patterned electrode film. By controlling the film thickness of each layer of the multilayer film used as the film material, the light absorptance of the irradiation laser light is controlled, and a polycrystalline silicon film having a uniform large grain size is formed within the substrate surface. The manufacturing method of the thin film semiconductor device in any one of Claims 12-14. The film thickness of each layer of the multilayer film used as the film material is controlled so that the light absorptance of the irradiation laser light is increased, and a polycrystalline silicon film having a uniform grain size within the substrate surface with a smaller irradiation laser light intensity. The method for manufacturing a thin film semiconductor device according to claim 12, wherein the method is formed. The pulse laser source is the second or third harmonic of a Q-switched Nd: YAG laser, the second or third harmonic of an Nd: glass laser, or the second or third harmonic of an Nd: YLF laser. A harmonic, a second harmonic or a third harmonic of a Yb: YAG or Yb: glass Yb ion-doped solid-state laser, or a fundamental wave or a second harmonic of a Ti: sapphire laser. The manufacturing method of the thin film semiconductor device in any one of 12-16. In a display device in which a thin film semiconductor element is provided on a display substrate, the thin film semiconductor element is formed on a substrate on which a light absorption layer patterned in a wiring shape including a gate electrode is formed via an insulating film. The semiconductor thin film is a film that is crystallized by laser annealing by irradiating a linear beam formed from a laser beam generated from a pulsed laser light source having a wavelength of 350 nm or more and 800 nm or less. A display device characterized by that. 19. The display device according to claim 18, wherein the insulating film is at least one film selected from a silicon oxide film and a silicon nitride film, and the semiconductor thin film is an amorphous silicon film. . 20. The display device according to claim 18, wherein an organic EL element connected to the thin film semiconductor element is provided on the display substrate. 21. The display device according to claim 18, wherein a pixel electrode for driving a liquid crystal is provided on the display substrate so as to be connected to the thin film semiconductor element. The pulse laser source is the second or third harmonic of a Q-switched Nd: YAG laser, the second or third harmonic of an Nd: glass laser, or the second or third harmonic of an Nd: YLF laser. A harmonic, a second harmonic or a third harmonic of a Yb: YAG or Yb: glass Yb ion-doped solid-state laser, or a fundamental wave or a second harmonic of a Ti: sapphire laser. The display device according to any one of 18 to 21. In a method for manufacturing a display device in which a thin film semiconductor element is provided on a display substrate,
A thin film semiconductor element is formed by providing a semiconductor thin film through an insulating film on a substrate on which a light absorption layer patterned into a wiring shape including a gate electrode is formed, and the wavelength of the semiconductor thin film is 350 nm to 800 nm. A method for manufacturing a display device, characterized in that a linear beam formed by a laser beam generated from a pulsed laser light source is irradiated and laser annealed to crystallize. 24. The display device according to claim 23, wherein the insulating film is at least one film selected from a silicon oxide film and a silicon nitride film, and the semiconductor thin film is an amorphous silicon film. Manufacturing method. 25. The method of manufacturing a display device according to claim 23, wherein an organic EL element is formed on the display substrate by being connected to the thin film semiconductor element. 26. The method for manufacturing a display device according to claim 23, wherein a pixel electrode for driving a liquid crystal is formed on the display substrate so as to be connected to the thin film semiconductor element. The pulse laser source is the second or third harmonic of a Q-switched Nd: YAG laser, the second or third harmonic of an Nd: glass laser, the second or third harmonic of an Nd: YLF laser. A harmonic, a second harmonic or a third harmonic of a Yb: YAG or Yb: glass Yb ion-doped solid-state laser, or a fundamental wave or a second harmonic of a Ti: sapphire laser. The manufacturing method of the display apparatus in any one of 23-26.

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