JP2005150438A - Manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device which is capable of manufacturing a stabilized thin film transistor with high characteristics, since a crystalline semiconductor film formed by utilizing a lateral growth method employing a capping method is constituted of a crystal excellent in crystallinity. <P>SOLUTION: The manufacturing method of semiconductor device is provided with a substrate and the crystalline semiconductor film laminated directly or indirectly on the substrate. The method comprises a process for laminating an amorphous semiconductor film directly or indirectly on the substrate, a process for laminating a first cap film and a second cap film which are in a specialized positional relation mutually on the surface of the amorphous semiconductor film, a process for melting a part of the amorphous semiconductor film in solid state into liquid state by irradiating laser light on the cap films, and a process for crystallizing the liquid state semiconductor to change the same into the crystalline semiconductor film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device. The present invention relates to a semiconductor device manufacturing method for manufacturing a semiconductor device such as a thin film transistor having a crystalline semiconductor film by crystallizing an amorphous semiconductor film using a laser.

  Thin film transistors (TFTs) used for display devices using liquid crystal or electroluminescence (EL) often use amorphous or crystalline silicon as an active layer. Among these, a crystalline silicon thin film transistor such as polycrystalline silicon or single crystal silicon has many advantages over an amorphous silicon thin film transistor because of high electron mobility.

  For example, when a crystalline silicon thin film transistor is used, not only can a switching element be formed in the pixel portion of the display device, but also a drive circuit and a peripheral circuit can be formed in the pixel peripheral portion. Can be formed on a single substrate. For this reason, it is not necessary to separately mount a driver IC or a drive circuit board on the display device, and it is possible to provide these display devices at a low price. In addition, since the size of the transistor can be reduced, a switching element formed in the pixel portion can be reduced, and a high aperture ratio of the display device can be achieved. Therefore, it is possible to provide a display device with high brightness and high definition.

  As a method for producing a crystalline silicon thin film such as polycrystalline silicon or single crystal silicon, a recrystallization technique using a laser beam has been proposed for a long time. For example, it is deposited on a substrate (amorphous silicon). There is a method of crystallizing (ELC, Excimer Laser Crystallization) by irradiating an excimer laser on an amorphous silicon film (including a film, a microcrystalline silicon film, and a polycrystalline silicon film having low crystallinity).

  The ELC method is generally a method of continuously irradiating a semiconductor film with a linear laser beam having a length of about 200 to 400 mm and a width of about 0.2 to 1.0 mm while scanning a sample at a constant speed. It is. At this time, the portion of the semiconductor film irradiated with the laser does not generally melt over the entire thickness direction, but melts while leaving a part of the semiconductor film region. For this reason, crystal nuclei are generated everywhere on the entire unmelted region / melted region interface, crystals grow toward the outermost layer of the semiconductor film, and crystal grains with random orientation are formed. In many cases, it becomes very small as 100 to 200 nm.

  A large number of unpaired electrons are present in the crystal grain boundary of the polycrystalline silicon film, so that a potential barrier is formed and acts as a strong carrier scatterer. Therefore, a TFT formed with a polycrystalline silicon film having a smaller crystal grain boundary, that is, a larger crystal grain size generally has a higher field effect mobility.

  However, in the conventional ELC method, as described above, since it is longitudinal crystal growth in which crystallization occurs at random positions at the unmelted region / melted region interface, it is difficult to obtain a polycrystalline silicon film having a large grain size. Therefore, it has been difficult to obtain a TFT having a high field effect mobility. In addition, due to crystallization at random, non-uniformity occurs in the film structure between the TFTs, which causes a problem that non-uniformity in switching characteristics occurs in the TFT array. In addition, when such a problem occurs, in the TFT liquid crystal display device, there arises a problem that pixels having a high display speed and pixels having a low display speed coexist in one display screen.

  Therefore, in order to obtain a higher performance TFT liquid crystal display device, it is necessary to increase the crystal grain size of the polycrystalline silicon film and to control the orientation of the silicon crystal. Therefore, many proposals have been made for the purpose of obtaining a polycrystalline silicon film having performance close to that of single crystal silicon.

  Among them, laser crystallization techniques classified as “lateral growth methods” are particularly attracting attention because long crystals having a uniform orientation in the crystal growth direction can be obtained.

  In one of the above lateral growth methods, either an antireflection film or a light shielding film for laser light used for crystallization is formed on a semiconductor film, and the semiconductor film is irradiated with laser light through these films. There is a method of performing crystallization by melting and solidifying the semiconductor film (also referred to as “capping method” in this specification) (see, for example, Patent Document 1 and Patent Document 2). This method is characterized in that not only a crystal having a large particle diameter can be obtained, but also the position control of the crystallized region becomes easy.

  FIG. 3 is a configuration diagram showing an example of a semiconductor device manufacturing apparatus used in the lateral growth method. In this method, a semiconductor device manufacturing apparatus 200 as shown in FIG. 3 irradiates a semiconductor film with a pulse laser and melts and solidifies a part of the semiconductor film over the entire thickness direction of the laser irradiation region to perform crystallization. Is. According to the semiconductor device manufacturing apparatus 200, the upper surface of the semiconductor device 1 is irradiated with the laser light emitted from the laser oscillator 11.

  FIG. 6 is a cross-sectional view of an example of a semiconductor device that is being fabricated by a conventional lateral growth method. Here, as shown in FIG. 6, the semiconductor device 1 includes a substrate 2, a buffer film 5, an amorphous semiconductor film 3, and a cap film 6. At this time, when the cap film 6 has an antireflection effect on the laser light, when the laser irradiation is performed such that the area of the laser light irradiation region C is larger than the area of the region where the cap film 6 is formed, More laser light 8 is absorbed in the amorphous semiconductor film 3 in the region where the cap film 6 is formed than in the amorphous semiconductor film 3 in the region where the cap film 6 is not formed. For this reason, heat is preferentially induced in the region of the amorphous semiconductor film 3 where the cap film 6 is formed by laser irradiation. Thereby, the amorphous semiconductor film 3 in the region where the cap film 6 is formed in the laser light irradiation region C can be melted over the thickness.

  Next, when the melted amorphous semiconductor film 3 is solidified by cooling, the melted region of the laser light irradiation region C is melted over the thickness. A crystal grows in the lateral direction from the boundary with the non-existing region toward the center of the cap film 6.

  As described above, according to the lateral growth method using the conventional capping method, the region for forming the crystalline semiconductor film and the orientation of the crystal growth direction are controlled by forming a cap film at a specific position. The channel region of the thin film transistor can be formed in a specific place.

  However, when a channel region is formed on a crystalline semiconductor film grown by a lateral growth method using a conventional capping method and a thin film transistor is manufactured, the thin film transistor has a difference in position where the channel region of the thin film transistor is formed. Many problems that caused variations in characteristics occurred.

  The cause of such variations in the characteristics of thin film transistors is that the crystal nuclei, which are the starting points for crystal growth by the lateral growth method, are generated at random positions on the boundary between the melted region and the non-melted region of the amorphous semiconductor film. That is, the size and width of the crystal constituting the crystalline semiconductor film forming the region differ depending on the position in the crystallization region of the semiconductor film.

Therefore, even when the channel region is formed on the crystalline semiconductor film grown by the lateral growth method using the conventional capping method described above and the thin film transistor is formed, the position control of the crystallization region is facilitated, A thin film transistor having stable characteristics with high channel region crystallinity and excellent field effect mobility has not yet been obtained.
JP 58-184720 A JP 2000-260709 A

  As described above, the lateral growth method using the conventional capping method makes it easy to control the position of the crystallized region. However, even if the channel region is formed using the obtained crystal, it has stable and high characteristics. There was a problem that a thin film transistor could not be obtained.

  In view of the above problems, the problem to be solved by the present invention is that a crystalline semiconductor film formed using a lateral growth method using a capping method is composed of crystals having excellent crystallinity. It is an object of the present invention to provide a method for manufacturing a semiconductor device capable of stably manufacturing a thin film transistor having high characteristics.

  In order to solve the above-mentioned problems, the present inventor further examined the problems of the lateral growth method using the conventional capping method.

  As a result, in the lateral growth method using the conventional capping method, the present inventor has found that the outermost layer of the amorphous semiconductor film melted from the substrate due to the presence of the cap film on the surface of the amorphous semiconductor film. It has been found that since the crystal growth in the direction toward is suppressed, a large internal stress is generated in the grown crystal, and in order to relieve this stress, a large number of subgrain boundaries are formed inside the crystal. The inventor has come to the conclusion that the characteristics of the thin film transistor are deteriorated because the large number of subgrain boundaries cause carrier scattering.

  Therefore, the present inventor tried to improve the lateral growth method using the capping method in order to solve the above problem of generation of subgrain boundaries, and repeated trial and error.

  As a result, the present inventor laminated the first cap film and the second cap film, which are in a specific positional relationship with each other, on the surface of the amorphous semiconductor film, thereby The inventors have found that a region having high crystallinity that can be suitably used for a channel region of a thin film transistor can be formed in a region sandwiched between second cap films, and the present invention has been completed.

  That is, the method for manufacturing a semiconductor device of the present invention is a method for manufacturing a semiconductor device comprising a substrate and a crystalline semiconductor film laminated directly or indirectly on the substrate, and directly or indirectly on the substrate. Laminating an amorphous semiconductor film on the surface, forming a first cap film on a portion of the surface of the amorphous semiconductor film, and forming the first cap film on the surface of the amorphous semiconductor film. A step of forming a second cap film on a part of the region where the cap film is not formed, and both the first cap film and the second cap film of the surface of the amorphous semiconductor film A portion of the amorphous semiconductor film in a solid state is melted into a liquid state by irradiating the region including the first cap film and the second cap film with laser light. And the liquid state semiconductor And a step of converting crystallized this crystalline semiconductor film, a manufacturing method of a semiconductor device.

  Here, the step of melting the amorphous semiconductor film into a liquid state includes the region where the first cap film and the second cap film are formed, the first cap film, and the second cap film. A region sandwiched between the cap films, and a region where the first cap film and the second cap film are formed and the first cap film is melted over the thickness of the amorphous semiconductor film. In addition, a region other than the region sandwiched between the second cap films and a region other than the region that does not melt over the thickness of the amorphous semiconductor film is irradiated with laser light of irradiance and irradiation time on the surface of the amorphous semiconductor film. By irradiating the region including both the first cap film and the second cap film, the first cap film, and the second cap film, Amorphous A part of the semiconductor film preferably includes a step of melting to a liquid state.

  Further, the step of converting to the crystalline semiconductor film includes the step of converting the region of the amorphous semiconductor film including both the first cap film and the second cap film, and the first cap film. In addition, it is desirable to include a step of crystallizing the liquid semiconductor and converting it into the crystalline semiconductor film in a state where the second cap film is irradiated with the second laser light.

  Then, the step of converting to the crystalline semiconductor film includes the step of converting the region of the surface of the amorphous semiconductor film including both the first cap film and the second cap film, and the first cap film. And the second cap film, in the case of irradiating alone, the second laser under the conditions of irradiance and irradiation time in which the amorphous semiconductor film cannot be heated to a temperature higher than the melting point. It is preferable to include a step of crystallizing the liquid semiconductor and converting it to the crystalline semiconductor film in the state of irradiation with light.

  In addition, the step of melting the amorphous semiconductor film into a liquid state includes a region including both the first cap film and the second cap film on the surface of the amorphous semiconductor film, By irradiating the first cap light and the second laser light to one cap film and the second cap film, a part of the amorphous semiconductor film in a solid state is liquidated The step of converting into a crystalline semiconductor film includes the step of melting into a state, and the step of converting to a crystalline semiconductor film by crystallizing the liquid state semiconductor in the state irradiated with the second laser light. It is desirable to include.

  Further, in the above case, the step of melting the amorphous semiconductor film into a liquid state includes a region including both the first cap film and the second cap film, and the first cap film. By irradiating the second cap film and the second laser beam having the irradiation region including the irradiation region of the first laser beam and the first laser beam, the second cap film is in a solid state. It is preferable to include a step of melting a part of the amorphous semiconductor film into a liquid state.

  The step of forming the first cap film includes a step of forming a first cap film having a reflectance lower than that of the amorphous semiconductor film with respect to the laser light. In the step of forming the cap film, a portion of the amorphous semiconductor film on the surface of the amorphous semiconductor film where the first cap film is not formed is partially exposed to the laser light. It is preferable to include a step of forming a second cap film having a reflectance lower than the reflectance.

  The step of forming the second cap film preferably includes the step of forming a second cap film in which at least a part of the boundary surface facing the first cap film is concave.

  Further, in the semiconductor device manufacturing method of the present invention, in addition to the above steps, the channel region of the thin film transistor is formed in a region of the crystalline semiconductor film where the first cap film and the second cap film are not formed. It is preferable to further include the step of performing.

  Further, it is desirable that the step of converting into the crystalline semiconductor film includes a step of crystallizing the liquid semiconductor to convert it into a single crystalline semiconductor film and / or a polycrystalline semiconductor film.

  Then, the step of laminating the amorphous semiconductor film is performed directly or indirectly on the substrate. The polycrystalline semiconductor film, the microcrystalline semiconductor film, and the amorphous semiconductor are lower in crystallinity than the crystalline semiconductor film. It is preferable to include a step of laminating one or more selected from the group consisting of films.

  The step of laminating the amorphous semiconductor film preferably includes a step of laminating an amorphous semiconductor film containing a silicon-based semiconductor as a material directly or indirectly on the substrate.

  The step of forming the first cap film includes the step of forming the first cap film containing silicon dioxide as a material, and the step of forming the second cap film includes the amorphous semiconductor film. It is preferable to include a step of forming a second cap film containing silicon dioxide as a material on a part of the surface where the first cap film is not formed.

  In the step of forming the second cap film, the first cap film and the second cap film are formed on a portion of the surface of the amorphous semiconductor film where the first cap film is not formed. It is desirable to include a step of forming the second cap film at a position where the shortest distance to the cap film is longer than the width of the channel region of the thin film transistor.

  The semiconductor device manufacturing method of the present invention uses the first cap film and the second cap film laminated on the surface of the amorphous semiconductor film so as to have a specific positional relationship with each other. Thus, in the region sandwiched between the first cap film and the second cap film, a region having a crystallinity high enough to be suitably used for a channel region of a thin film transistor and including no sub-boundary is produced. Can do.

  That is, by using the semiconductor device manufacturing method of the present invention, even when a crystalline semiconductor film is formed using a lateral growth method using a capping method, a semiconductor composed of crystals having excellent crystallinity. A membrane can be obtained. Therefore, a thin film transistor having a high characteristic can be stably provided by forming a thin film transistor on a crystal that does not include a sub-boundary.

  Hereinafter, the present invention will be described in more detail with reference to embodiments.

<Semiconductor device manufacturing method>
FIG. 1 is a flow chart showing steps of an example of a method for manufacturing a semiconductor device of the present invention.

  The semiconductor device manufacturing method of the present invention is, for example, as shown in FIG. 1, a semiconductor device manufacturing method comprising a substrate and a crystalline semiconductor film laminated directly or indirectly on the substrate, A step of laminating an amorphous semiconductor film directly or indirectly on the substrate (S101), a step of forming a first cap film on a part of the surface of the amorphous semiconductor film (S103), A step (S105) of forming a second cap film on a portion of the surface of the amorphous semiconductor film where the first cap film is not formed; The solid state is obtained by irradiating the region including both the first cap film and the second cap film, the first cap film, and the second cap film with laser light. Of this amorphous semiconductor film Parts and step (S107) is melted to a liquid state, the semiconductor of the liquid state by crystallizing comprises a step (S109) of converting into the crystalline semiconductor film, the a method for manufacturing a semiconductor device.

  The reason why the semiconductor device manufacturing method of the present invention includes the plurality of steps described above is that the first cap film laminated on the surface of the amorphous semiconductor film so as to have a specific positional relationship with each other, and When the second cap film is laminated, the crystallinity can be suitably used for the channel region of the thin film transistor in the region sandwiched between the first cap film and the second cap film by irradiating laser light. This is because a region that is high and does not include subgrain boundaries can be produced.

<Thin film lamination process>
FIG. 2 is a cross-sectional view showing a process of an example of a method for manufacturing a semiconductor device of the present invention.

  In this example, in accordance with the procedure shown in FIG. 2, a plurality of thin films are sequentially stacked on the substrate 2 for manufacturing the semiconductor device 1.

  First, as shown in FIG. 2A, the amorphous semiconductor film 3 is formed directly or indirectly on the substrate 2. Here, the substrate 2 is preferably insulative, and a glass substrate, a quartz substrate, or the like can be used. However, it is preferable to use a glass substrate because it is inexpensive and can easily manufacture a large area substrate. is there.

  The amorphous semiconductor film 3 is preferably laminated by a plasma enhanced chemical vapor deposition (PECVD) method, a vapor deposition method, a sputtering method or the like so that the film thickness is in the range of 10 nm to 100 nm.

  The material of the amorphous semiconductor film 3 is not particularly limited as long as it is a conventionally known material that exhibits semiconductor characteristics, but amorphous silicon whose various characteristics are remarkably improved by increasing the length of lateral crystal growth. A film is preferred. The material of the amorphous semiconductor film 3 is not limited to a material made only of silicon, and may be a material mainly composed of silicon containing other elements such as germanium. Among these, it is particularly desirable to include silicon dioxide as a material.

  The first cap film preferably has a reflectance lower than that of the amorphous semiconductor film with respect to the laser light. Further, the second cap film is formed on a part of the surface of the amorphous semiconductor film where the first cap film is not formed, and the reflectance of the amorphous semiconductor film with respect to the laser light It is preferred to have a lower reflectivity. If the cap film has a low reflectance with respect to the laser beam, the absorption of the laser beam is increased. Therefore, the amorphous semiconductor film in the lower portion of the cap film and its peripheral region is heated better than the other regions, and it is easy and short. This is because only the target region melts in time.

  Here, a buffer film 5 may be formed between the substrate 2 and the amorphous semiconductor film 3 as shown in FIG. By forming the buffer film 5, it is possible to prevent the thermal effect of the melted amorphous semiconductor film 3 from affecting the substrate 2 mainly during melting and recrystallization by laser light. Diffusion of impurities into the amorphous semiconductor film 3 can be prevented. As such a buffer film 5, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, etc., which are stacked by a vapor deposition method, an ion plating method, a sputtering method, or the like within a range of 100 to 300 nm. Is mentioned.

  Next, as shown in FIG. 2B, the cap film 6 including the first cap film 30 and the second cap film 31 is formed on the amorphous semiconductor film 3. The cap film 6 is laminated by a plasma enhanced chemical vapor deposition (PECVD) method, a vapor deposition method, a sputtering method, or the like. The material of the cap film 6 is not particularly limited as long as it does not melt with respect to the laser beam irradiated in the subsequent process. However, from the viewpoint of the stability of the material and the ease of designing the film thickness, silicon dioxide is used. The main material is desirable.

  FIG. 8 is a plan view showing an example of a method for forming a cap film used in the present invention.

  Here, as shown in FIG. 8, the cap film 6 to be formed is composed of a first cap film 30 and a second cap film 31 having a predetermined shape and a specific positional relationship. That is, the second cap film is preferably formed such that at least a part of the boundary surface facing the first cap film is concave. As will be described later, since the melted amorphous semiconductor film starts crystal growth with a concave portion as a nucleus, a large single crystal region can be obtained without much crystal growth occurring randomly. It is.

  The shortest length 34 between the first cap 30 and the second cap film 31 is preferably 1 or more times the width of the channel region of the thin film transistor, and more preferably 1.5 times or more. This is because when the length is too small, a region that is not a single crystal tends to be included in the channel region.

  Even within these ranges, the shortest length 34 between the first cap 30 and the second cap film 31 is about twice as long as a length sufficient to form a channel region when a thin film transistor is formed. Most preferred. Since a large single crystal region grows in a region where the first cap film and the second cap film are not formed between the first cap and the second cap film as will be described later, a thin film transistor is formed in this region. This is because a thin film transistor having excellent characteristics can be manufactured by forming the channel region.

  Thereafter, as shown in FIG. 2C, the process proceeds to the step of irradiating the amorphous semiconductor film 3, the first cap film 30, and the second cap film 31 with the laser light 8, but the details are as follows. Is described below.

<Semiconductor film crystallization process>
FIG. 3 is a block diagram showing an example of a semiconductor device manufacturing apparatus used for the lateral growth method.

  In the semiconductor device manufacturing method of the present invention, following the above-described thin film stacking step, the stacked amorphous semiconductor film is crystallized using a semiconductor device manufacturing apparatus as shown in FIG. Is preferably formed.

  This is because the semiconductor device manufacturing apparatus as shown in FIG. 3 includes both the first cap film and the second cap film among the surfaces of the amorphous semiconductor film provided in the semiconductor device manufacturing method of the present invention. A step of melting a part of the amorphous semiconductor film in a solid state into a liquid state is performed by irradiating the region, the first cap film, and the second cap film with laser light. It is because it is suitable for.

  First, FIG. 3 shows a conceptual diagram of a semiconductor device manufacturing apparatus 200 for crystallizing an amorphous semiconductor film. A laser oscillator 11, a variable attenuator 12, a field lens 13, a mask 14, an imaging lens 15, A sample stage 16 and several mirrors 10a, 10b, 10c are included. The laser oscillator 11 and the sample stage 16 are controlled by a controller 17, and the laser irradiation timing and the position of the sample stage 16 can be adjusted. Thereby, in the said apparatus, the area irradiated with a laser beam can be moved by moving the sample stage 16 to the arrow direction in a figure. By using this semiconductor device manufacturing apparatus 200, the laser beam 18 can be supplied to the semiconductor device 1 on the stage 16.

  The laser beam 18 preferably has a wavelength in a range where the absorption rate into the amorphous semiconductor film 3 in a solid state is high. Specifically, the laser oscillator 11 is desirably a laser oscillator 11 having a wavelength in the ultraviolet region, such as various solid-state lasers typified by excimer lasers and YAG lasers. Of these, the excimer laser oscillator 11 having a wavelength of 308 nm capable of pulse radiation is particularly preferable.

  Further, the laser light preferably has at least irradiance and irradiation time for melting the amorphous semiconductor film in the region where the cap film is formed in a solid state. The irradiance and irradiation time vary depending on the material of the semiconductor film, the thickness of the semiconductor film, the area of the crystallization region, the reflectance of the cap film with respect to the laser light, and the like, and cannot be uniquely determined. It is desirable to use the first laser beam 18 having an appropriate irradiance and irradiation time according to the embodiment. Specifically, the amorphous semiconductor film in the region where the cap film is formed by one irradiation can be heated to a temperature equal to or higher than the melting point in the entire film thickness, and the cap film is not formed. It is recommended to use the first laser beam 18 having an irradiance and an irradiation time that cannot heat the amorphous semiconductor film in the region to a temperature equal to or higher than the melting point in the entire film thickness.

  Here, in the surface of the amorphous semiconductor film, the region including both the first cap film and the second cap film is a peripheral region of the first cap film and a peripheral region of the second cap film. And a region including a region sandwiched between the first cap film and the second cap film.

  At this time, laser light is applied to the region including both the first cap film and the second cap film, the first cap film, and the second cap film on the surface of the amorphous semiconductor film. Is irradiated to the peripheral region of the first cap film, the peripheral region of the second cap film, the first cap film, and the second cap film. Become.

  In addition, among the regions including both the first cap film and the second cap film in the surface of the amorphous semiconductor film, the region where the first cap film and the second cap film are stacked is a laser. Light is not directly irradiated. This is because the first cap film and the second cap film exist in the middle of the laser irradiation path.

  FIG. 4 is a configuration diagram showing an example of a semiconductor device manufacturing apparatus used in the lateral growth method.

  The semiconductor device manufacturing apparatus used in the present invention may be a semiconductor device apparatus 202 having a first laser beam 18 and a second laser beam 19 as shown in FIG.

  The first laser beam 18 preferably has a wavelength in a range in which the absorptance to the amorphous semiconductor film in a solid state is higher than that of the second laser beam 19.

  As the laser oscillator, the first laser oscillator 20 used for the first laser beam 18 desirably has an ultraviolet wavelength such as an excimer laser or various solid-state lasers typified by a YAG laser. Among these, the first excimer laser oscillator 20 having a wavelength of 308 nm capable of pulse radiation is particularly preferable.

  Further, the first laser beam 18 has at least irradiance and irradiation time for melting the amorphous semiconductor film in the region where the cap film is formed, which is in a solid state. The amount of energy varies depending on the material of the semiconductor film, the thickness of the semiconductor film, the area of the crystallization region, the reflectance of the cap film with respect to the laser light, and the like, and cannot be uniquely determined. It is desirable to use the first laser beam 18 having appropriate irradiance and irradiation time as appropriate. Specifically, the amorphous semiconductor film in the region where the cap film is formed can be heated to a temperature equal to or higher than the melting point in the entire film thickness by one irradiation, and the cap film is formed. It is recommended to use the first laser beam 18 having an irradiance and an irradiation time that cannot heat the amorphous semiconductor film in a region not present to a temperature equal to or higher than the melting point in the entire film thickness.

  The second laser beam 19 preferably has a wavelength in a range where the absorption rate of the amorphous semiconductor film in a liquid state is higher than that of the first laser beam 18.

  As the oscillator, the second laser oscillator 21 used for the second laser light 19 preferably has a wavelength in the visible region to the infrared region. Examples include a YAG laser having a wavelength of 532 nm, a YAG laser having a wavelength of 1064 nm, and a second laser oscillator 21 that can emit a carbon dioxide gas laser having a wavelength of 10.6 μm.

  Further, the second laser beam 19 has an irradiance and an irradiation time that do not melt the amorphous semiconductor film in the solid state. This amount of energy varies depending on the material of the semiconductor film, the film thickness of the semiconductor film, the area of the crystallization region, and the like, and cannot be uniquely determined. It is desirable to use the second laser beam 19 for the irradiation time. Specifically, when the second laser beam 19 is irradiated alone, the second laser beam 19 having an irradiance and an irradiation time that cannot heat the amorphous semiconductor film to a temperature higher than the melting point is applied. Recommended to use.

  That is, the second laser beam used in the present invention is preferably a laser beam under conditions of irradiance and irradiation time in which the amorphous semiconductor film cannot be heated to a temperature higher than the melting point in the case of single irradiation. . This is because the second laser beam is irradiated for the purpose of reducing the temperature drop rate of the semiconductor and extending the time until solidification.

  In the present embodiment, for example, the first laser beam 18 can be incident from the vertical direction, and the second laser beam 19 can be incident from the oblique direction.

  Further, the irradiation region of the second laser beam 19 is preferably an irradiation region including an irradiation region of the first laser beam 18 and having a larger area than the irradiation region of the first laser beam 18.

  In FIG. 4, the variable attenuator 25 and the mirrors 10a, 10b, 10c, and 10d are shown for explanation.

  FIG. 5 is a graph for explaining an example of a laser beam irradiation method when the semiconductor device manufacturing method of the present invention is carried out.

  The relationship between the irradiation time of the first laser beam and the second laser beam and the output is preferably the same as the relationship shown in FIG. Here, the pulse waveform 23 of the first laser beam indicates that the irradiation of the first laser beam starts at time t = 0, and the pulse waveform 24 of the second laser beam indicates that the second laser beam is In the time excluding time t = t1 to t2, it is emitted with low output (with low irradiance), and with high output (with high irradiance) at time t = t1 to t2.

  At time t1, the amorphous semiconductor film is melted and in a liquid state. The amorphous semiconductor film in the liquid state is irradiated with the second laser beam in addition to the first laser beam at a high output, so that the temperature drop rate of the semiconductor can be reduced and solidified. Therefore, the length of crystal growth of crystals constituting the crystalline semiconductor film generated by solidification of the amorphous semiconductor film in a liquid state can be greatly extended.

  Therefore, the step of melting the amorphous semiconductor film into a liquid state includes a region including both the first cap film and the second cap film on the surface of the amorphous semiconductor film, and the first cap. It is preferable to include a step of crystallizing a liquid semiconductor to convert it into a crystalline semiconductor film in a state where the film and the second cap film are irradiated with the second laser light.

<Crystallinity of semiconductor film>
The step of converting into a crystalline semiconductor film preferably includes a step of crystallizing a liquid semiconductor to convert it into a single crystalline semiconductor film and / or a polycrystalline semiconductor film. Note that in this specification, a crystalline semiconductor film is a concept including a single crystal semiconductor film and a polycrystalline semiconductor film, and indicates a semiconductor film including a semiconductor with high crystallinity as a main material. However, the crystalline semiconductor film does not necessarily have to be made entirely of a single crystal semiconductor or a polycrystalline semiconductor, and partially includes a material made of an amorphous semiconductor, a microcrystalline semiconductor, or a polycrystalline semiconductor having low crystallinity. However, it is only necessary to include a highly crystalline semiconductor as a main material.

  In addition, the step of laminating the amorphous semiconductor film includes a polycrystalline semiconductor film, a microcrystalline semiconductor film, and an amorphous semiconductor film having a lower crystallinity than the crystalline semiconductor film, directly or indirectly on the substrate. The process of laminating | stacking 1 or more types chosen from the group which consists of may be included. This is because even such an amorphous semiconductor film with low crystallinity can be easily and reliably converted into a crystalline semiconductor film by the above laser irradiation method. Note that in this specification, an amorphous semiconductor film is a concept including a polycrystalline semiconductor film having a lower crystallinity than a crystalline semiconductor film, a microcrystalline semiconductor film, an amorphous semiconductor film, and the like. A semiconductor film including a low-performance semiconductor as a main material is shown. However, an amorphous semiconductor film does not necessarily need to be made of a polycrystalline semiconductor film, a microcrystalline semiconductor film, an amorphous semiconductor film, or the like, in which all materials are completely low in crystallinity. Even if a material made of a crystalline semiconductor is included, it is only necessary to include a polycrystalline semiconductor film, a microcrystalline semiconductor film, an amorphous semiconductor film, or the like having a low crystallinity as a main material.

  Hereinafter, the present invention will be described in more detail with reference to embodiments, but the present invention is not limited thereto.

[Embodiment 1]
The following describes Embodiment 1 of the present invention.

  FIG. 2 is a cross-sectional view showing a process of an example of a method for manufacturing a semiconductor device of the present invention.

  First, according to the procedure shown in FIG. 2, a buffer film 5 made of a silicon dioxide film is formed on a substrate 2 made of a glass substrate, and an amorphous semiconductor film 3 made of an amorphous silicon film is formed on the silicon dioxide film. A cap film 6 containing silicon dioxide as a main component was formed on the amorphous silicon film.

  The silicon dioxide film is laminated with a film thickness of 300 nm on the glass substrate by vapor deposition, ion plating, sputtering, or the like. The amorphous silicon film is laminated with a thickness of 50 nm on the silicon dioxide film by plasma enhanced chemical vapor deposition (PECVD), vapor deposition, sputtering, or the like.

  The cap film 6 is formed by depositing a film having a thickness of 50 nm on the amorphous silicon film by vapor deposition, ion plating, sputtering, or the like, and then patterning the film into a predetermined shape and position by a photolithography process.

  FIG. 8 is a plan view showing an example of a method for forming a cap film used in the present invention.

  The cap film 6 to be formed is composed of a first cap film 30 and a second cap film 31 as shown in FIG.

  Here, it is desirable that the second cap film 31 is smaller than the first cap film 30 and has a predetermined distance from the first cap film 30. In addition, the second cap film 31 has a shape in which a part of the boundary facing the first cap film 30 has a concave shape (for example, a cutout shape having an inner angle of 45 degrees) in a top view shape. It is desirable. In the present embodiment, the first cap film 30 has a rectangular shape in which the first cap film length 32 is 50 μm and the first cap film width 33 is 20 μm. The shape of the second cap film 31 was a shape having a cutout portion on one side facing the first cap film in a square pattern having a side length of 5 μm. At this time, the inner angle 35 of the notch included in the second cap film was set to 45 °. The shortest distance 34 between the first cap and the second cap film was 16 μm.

  FIG. 3 is a block diagram showing an example of a semiconductor device manufacturing apparatus used for the lateral growth method.

Next, using the apparatus shown in FIG. 3, the amorphous silicon film is irradiated with laser light through the cap film to convert the amorphous silicon film into a polycrystalline silicon film. An excimer laser was used as the laser beam, the wavelength was 308 nm, the energy fluence of one irradiation was ² kJ / m ² , the irradiation time was about 50 ns, and the size of the irradiation region was (5 mm × 5 mm). In this embodiment mode, laser light irradiation is performed in a state where the temperature of the substrate in a region other than the region irradiated with laser light is maintained at a temperature equivalent to room temperature (25 ° C.).

  FIG. 7 is a graph illustrating that the reflectance with respect to laser light having a wavelength of 308 nm depends on the film thickness of a cap film made of a silicon dioxide film.

  Here, when laser irradiation is performed on the silicon film through the cap film, the reflectance changes depending on the wavelength of the laser, the material of the cap film, the film thickness of the silicon film, and the like. FIG. 7 shows changes in the reflectance of an excimer laser having a wavelength of 308 nm with respect to the film thickness of a cap film made of a silicon dioxide film formed on silicon having a thickness of 50 nm.

  When the thickness of the cap film is 100 nm, the reflectance with respect to the laser beam is maximized, and when the thickness of the cap film is 50 nm, the reflectance with respect to the laser beam is minimized. Accordingly, when a cap film having a film thickness of 50 nm is formed on the amorphous silicon film, the reflectance is minimized, so that more laser light is absorbed and the region where the cap film is formed is selectively heated. be able to.

  In addition, a polycrystalline silicon film was formed in accordance with this embodiment, and a polycrystalline silicon film was formed in the following steps according to a conventional capping method. An amorphous silicon film having a thickness of 50 nm is formed on a glass substrate, a cap film made of silicon dioxide having a thickness of 50 nm is formed on the amorphous silicon film, and then a polycrystalline silicon film is formed by laser irradiation. Formed. The method for forming a thin film, the semiconductor device manufacturing apparatus, the laser irradiation method, and the like are the same as those in this embodiment, and are omitted.

  FIG. 9A is a schematic diagram of a film surface image obtained by photographing a film surface of an example of a crystalline semiconductor film included in a semiconductor device obtained by the semiconductor device manufacturing method of the present invention by SEM. FIG. 9B is a schematic diagram of a film surface image obtained by photographing a film surface of an example of a crystalline semiconductor film obtained by a conventional lateral growth method by SEM.

  Next, in order to compare the crystallinity of the silicon film according to the present embodiment and the silicon film according to the conventional technique, crystal observation is performed by SEM (Scanning Electron Microscope). First, SECCO etching is performed on each polycrystalline silicon film. FIG. 9 shows the result of magnifying and observing the silicon film treated in this way by SEM. FIG. 9A is a film surface image obtained by photographing the film surface of the polycrystalline silicon film according to the present embodiment with the SEM, and FIG. 9B is a film surface image of the polycrystalline silicon film according to the prior art with the SEM. It is the film | membrane surface image which image | photographed. In FIG. 9, the second cap film and the crystal growing in the second cap film are omitted.

  As shown in FIG. 9B, the polycrystalline silicon film according to the prior art is composed of a normal crystal 37 having a length of about 11 μm and a width of about 1 μm, and the normal crystal 37 is slightly in the region where the cap film is formed. It is formed from the outside to the center of the cap film.

  Here, in the prior art, since the laser beam is also irradiated to the region where the cap film is not formed, the laser beam energy is converted into thermal energy, although it is not as efficient as the region where the cap film is formed. Is done. Further, thermal energy generated in the region where the cap film is formed during the laser light irradiation diffuses to the region where the cap film is not formed. As a result, a region where the amorphous silicon film melts over the thickness is formed near the interface between the region where the cap film is formed and the region where the cap film is not formed.

  For this reason, the area | region which fuse | melts over a thickness spreads to the some outer side of the area | region in which the cap film is formed. Therefore, the starting point 40 of the normal crystal, which is the boundary between the region melted over the thickness and the region not melted over the thickness, is formed slightly outside the region where the cap film is formed. The Then, crystal growth occurs from the position of the starting point 40 of the normal crystal into the cap film, collides with the crystal grown from the opposite irradiation region end, and the growth ends.

  Of the crystals grown in this manner, the crystal grown in the region where the first cap film 30 is formed includes a large number of subgrain boundaries 39 in the crystal grains. Those grown in a region where no is formed do not include subgrain boundaries 39 in the crystal grains.

  This is because, in the region where the first cap film 30 is formed, growth in the direction from the substrate toward the outermost layer of the semiconductor film is suppressed, so that a large internal stress is generated in the growth crystal and this stress is relieved. For this reason, while a large number of subgrain boundaries 39 are formed inside the crystal, growth in the direction from the substrate toward the outermost layer of the semiconductor film is not suppressed in the region where the first cap film 30 is not formed. This is because the internal stress is very small and the subgrain boundaries 39 are not formed inside the crystal.

  The crystal growing in the region where the cap film is not formed tends to increase, for example, by increasing the energy of the irradiated laser beam. However, when laser light is irradiated with excessive energy, the silicon film in the region where the cap film is formed explodes (ablates), and as a result, the number of crystals growing in the region where the cap film is not formed increases so much. I can't.

  In the case of the prior art, the region not including the sub-boundary 39 is very narrow, about 1 μm in length and about 1 μm in width, and is not wide enough to form a channel region and form a thin film transistor. Therefore, the channel region of the thin film transistor is formed on the normal crystal 37 including many subgrain boundaries 39. Such a thin film transistor has significantly low characteristics because carrier scattering occurs at the subgrain boundaries 39.

  On the other hand, as shown in FIG. 9A, the polycrystalline silicon film according to the present embodiment has a large crystal having a length of about 18 μm and a width of about 3 μm in addition to a normal crystal 37 having a length of about 11 μm and a width of about 1 μm. 38, each crystal is formed from the outside of the region where the first cap film 30 is formed to the center of the first cap film 30. In comparison, growth is taking place from the outside.

  The reason why the large crystal 38 is formed is as follows.

  Since the crystallization is performed by the capping method, in the present embodiment as well, as in the conventional technique, the melted region spreads over the thickness slightly outside the region where the cap film is formed. However, in the case of this embodiment, since the second cap film 31 is formed in addition to the first cap film 30, the second cap film 30 is not formed in the region where the first cap film 30 is not formed. The region in the vicinity of the cap film 31 is affected by thermal diffusion from the second cap film 31, and the region where the amorphous silicon film melts over the thickness further spreads toward the second cap 31 side. .

  As a result, as shown in FIG. 9A, the starting point 41 of the large crystal where the crystal nucleus is formed is formed closer to the second cap film 31 than the starting point 40 of the normal crystal. Then, crystal growth occurs from the position of the starting point 41 of the large crystal into the cap film, collides with the crystal grown from the opposite irradiation region end, and the growth ends.

  Further, since the second cap film 31 has a shape having a notch, a single nucleus is easily formed. Therefore, since the crystal grown from the starting point 41 of the large crystal can be grown without being hindered by the crystals formed around it, it can grow greatly in the width direction.

  Therefore, in the case of the present embodiment, it is possible to form a large crystal 38 that is expanded in both the length and width directions than the normal crystal 37.

  Among the large crystals 38 thus grown, those grown in the region where the first cap film 30 is formed, as in the case of the prior art, include a large number of subgrain boundaries 39 in the crystal grains. However, those grown in the region where the first cap film 30 is not formed do not include the subgrain boundaries 39 in the crystal grains.

  In the case of the present embodiment, the region not including the sub-boundary 39 is about 8 μm in length and about 3 μm in width, which is much wider than in the case of the prior art, which is sufficient for forming a thin film transistor that forms a channel region. It becomes a large area. Therefore, a thin film transistor can be formed on a region of the large crystal 38 that does not include the subgrain boundary 39.

  In the present embodiment, the second cap film 31 is a pattern having a notch, but the same effect may be obtained even when the shape, size, etc. are other than this.

  FIG. 10 is a diagram for explaining an example of a method for manufacturing a thin film transistor including, as an active layer, a crystalline semiconductor film included in a semiconductor device obtained by the method for manufacturing a semiconductor device of the present invention.

  First, the amorphous silicon film is crystallized by a lateral growth method using the capping method used in the semiconductor device manufacturing method of the present invention, and the cap film is removed by etching (FIG. 10A).

  Next, a silicon island region (activation layer) 45 is formed by photolithography (FIG. 10B). At this time, the silicon island region 45 is disposed so that the channel region 44 is configured only in a region where the first cap film 30 of the large crystal 38 is not formed.

  Next, after forming an insulating layer on the silicon film, a gate electrode 46 is formed (FIG. 10C), impurities are ion-implanted by an ion doping method, an activation process is performed, and then an interlayer insulating film is formed. Formation of the thin film transistor is completed by forming the contact hole and providing the electrode wiring. Note that hydrogenation treatment for improving transistor characteristics may be performed as necessary.

  FIG. 11 is a cross-sectional view illustrating an example of the structure of a thin film transistor obtained by the method for manufacturing a semiconductor device of the present invention.

  In FIG. 11, for explanation, a source electrode 61, a drain electrode 62, a gate electrode 63, a channel region 64, a silicon island region (active layer) 65, an insulating layer 66, a buffer layer (insulating layer) 67, an insulating substrate 68 is described.

  FIG. 12 is a diagram for explaining an example of a method of manufacturing a thin film transistor using a crystalline semiconductor film as an active layer by a conventional lateral growth method.

  A thin film transistor using a semiconductor device produced by a conventional technique is constituted by a region in which a first cap film 30 is formed in a crystalline semiconductor film in which a channel region 44 is grown. For this reason, the silicon film in the channel region 44 includes a large number of subgrain boundaries. Therefore, carrier scattering occurs at the grain boundary, and the performance of the thin film transistor is degraded. In addition, since the size and width of crystals forming the crystalline semiconductor film forming the channel region 44 vary depending on the position in the crystallization region, the transistor characteristics vary depending on the position where the channel region 44 of the thin film transistor is formed.

  On the other hand, in the thin film transistor using the semiconductor device manufactured according to the present embodiment, the channel region is formed of a region on the large crystal where the first cap film is not formed. For this reason, the silicon film in the channel region does not include subgrain boundaries. Such a thin film transistor has significantly improved characteristics as compared with the prior art because scattering of carriers at sub-grain boundaries is suppressed. Furthermore, since a large crystal is always formed between the first cap film and the second cap film, a high-performance thin film transistor can be obtained without fail if a thin film transistor is formed in this region.

  As described above, according to the present embodiment, a thin film transistor channel region is formed in a region where a sub-boundary is not formed in a large crystal, thereby stably providing a high-performance thin film transistor. Can do.

  That is, according to the present embodiment, the first cap film and the second cap film are formed on the amorphous silicon film, and the laser light is irradiated so as to include these cap films, so that the crystallinity is achieved. A crystalline semiconductor film composed of an excellent polycrystalline silicon film can be obtained. By forming the channel region of the thin film transistor on such a polycrystalline silicon film, a thin film transistor having high characteristics can be stably provided.

[Embodiment 2]
The following describes Embodiment 2 of the present invention.

  This embodiment is the same as the first embodiment except for the apparatus and laser irradiation method used for laser irradiation. Therefore, a detailed description of the same parts will be omitted, and a device used for laser irradiation and a laser irradiation method will be described in detail.

  FIG. 4 is a configuration diagram showing an example of a semiconductor device manufacturing apparatus used in the lateral growth method.

  In this embodiment, the apparatus shown in FIG. 4 is used instead of the apparatus shown in FIG. That is, the second laser irradiation is performed in addition to the first laser irradiation.

  FIG. 5 is a graph for explaining an example of a laser beam irradiation method when the semiconductor device manufacturing method of the present invention is carried out.

  In the present embodiment, the relationship between the irradiation time and the output of the first laser beam and the second laser beam shown in FIG. Were irradiated to the amorphous silicon film.

In the relationship between the irradiation time and the output of the first laser beam and the second laser beam shown in FIG. 5, an excimer laser is used as the first laser beam, the wavelength is 308 nm, and the irradiation is performed once. The energy fluence per unit is ² kJ / m ² , the irradiation time is about 50 ns, the size of the irradiation region is (5 mm × 5 mm), a carbon dioxide laser is used as the second laser beam, the wavelength is 10.6 μm, and the energy fluence. Was about 50 kJ / m ² , the irradiation time was about 3 ms, and the size of the irradiation region was (5.5 mm × 5.5 mm).

  Further, in the present embodiment, the substrate temperature in the region other than the region irradiated with the first laser beam and the second laser beam is maintained at a temperature equivalent to room temperature (25 ° C.). Irradiation with one laser beam and a second laser beam was performed.

  In the present embodiment, the first laser beam is incident from the vertical direction, and the second laser beam is incident at an angle of 30 degrees with the vertical direction.

  In this way, by irradiating the amorphous silicon film in the liquid state with the second laser light in addition to the first laser light, the temperature decrease rate of the silicon film can be reduced and solidified. Therefore, it is possible to efficiently obtain a polycrystalline silicon film having a larger grain size.

  FIG. 7 is a graph illustrating that the reflectance with respect to laser light having a wavelength of 308 nm depends on the film thickness of a cap film made of a silicon dioxide film.

  Here, when laser irradiation is performed on the silicon film through the cap film, the reflectance changes depending on the wavelength of the laser, the material of the cap film, the film thickness of the silicon film, and the like. FIG. 7 shows changes in the reflectance of an excimer laser having a wavelength of 308 nm with respect to the film thickness of a cap film made of a silicon dioxide film formed on silicon having a thickness of 50 nm.

  When the thickness of the cap film is 100 nm, the reflectance with respect to the laser beam is maximized, and when the thickness of the cap film is 50 nm, the reflectance with respect to the laser beam is minimized. As a result, when a cap film having a thickness of 50 nm is formed on the amorphous silicon film 3, the region where the cap film is formed can be selectively heated by laser irradiation.

  FIG. 9A is a schematic diagram of a film surface image obtained by photographing a film surface of an example of a crystalline semiconductor film included in a semiconductor device obtained by the semiconductor device manufacturing method of the present invention by SEM. FIG. 9B is a schematic diagram of a film surface image obtained by photographing a film surface of an example of a crystalline semiconductor film obtained by a conventional lateral growth method by SEM.

  In order to compare the crystallinity of the silicon film according to the present embodiment and the silicon film according to the prior art, when the crystal was observed by SEM (Scanning Electron Microscope), the polycrystalline silicon film according to the present embodiment is shown in FIG. The dimensions of the large crystal 38 shown in a) are about 20 μm in length and about 5 μm in width, and it was demonstrated that the crystal can be made larger than that in the first embodiment.

  As described above, according to the present embodiment, the first cap film and the second cap film are formed on the amorphous silicon film, and the laser light is irradiated so as to include these cap films. A semiconductor film composed of a polycrystalline silicon film having excellent crystallinity can be obtained. By forming the channel region of the thin film transistor on such a polycrystalline silicon film, a thin film transistor having high characteristics can be stably provided.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a flowchart which shows the process of an example of the manufacturing method of the semiconductor device of this invention. It is sectional drawing which shows the process of an example of the manufacturing method of the semiconductor device of this invention. It is a block diagram which shows an example of the semiconductor device manufacturing apparatus used for the lateral growth method. It is a block diagram which shows an example of the semiconductor device manufacturing apparatus used for the lateral growth method. It is a graph explaining an example of the irradiation method of the laser beam at the time of enforcing the manufacturing method of the semiconductor device of this invention. It is sectional drawing of an example of the semiconductor device in the middle of preparation in the conventional lateral growth method. It is a graph explaining that the reflectance with respect to the laser beam of wavelength 308nm depends on the film thickness of the cap film which consists of a silicon dioxide film. It is a top view which shows an example of the formation method of the cap film used for this invention. FIG. 9A is a schematic diagram of a film surface image obtained by photographing a film surface of an example of a crystalline semiconductor film included in a semiconductor device obtained by the semiconductor device manufacturing method of the present invention with an SEM, and FIG. ) Is a schematic diagram of a film surface image obtained by photographing a film surface of an example of a crystalline semiconductor film obtained by a conventional lateral growth method by SEM. It is a figure explaining an example of the thin-film transistor which uses the crystalline semiconductor film contained in the semiconductor device obtained by the manufacturing method of the semiconductor device of this invention as an active layer, and its manufacturing method. It is sectional drawing explaining an example of the structure of a thin-film transistor obtained by the manufacturing method of the semiconductor device of this invention. It is a figure explaining an example of the manufacturing method of the thin-film transistor which uses the crystalline semiconductor film as an active layer by the conventional lateral growth method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Semiconductor device, 2 Substrate, 3 Amorphous semiconductor film, 5 Buffer film, 6 Cap film, 8 Laser light, 10a, 10b, 10c, 10d Mirror, 11 Laser oscillator, 12 Variable attenuator, 13 Field lens, 14 Projection Mask, 15 Imaging lens, 16 Sample stage, 17 Controller, 18 First laser beam, 19 Second laser beam, 20 First laser oscillator, 21 Second laser oscillator, 23 Pulse of first laser beam Waveform, 24 Pulse waveform of the second laser light, 25 Variable attenuator, 30 First cap film, 31 Second cap film, 32 Length of the first cap film, 33 Width of the first cap film, 34 the shortest distance between the first cap film and the second cap film, 35 the inner angle of the notch portion of the second cap film, 37 the normal crystal 38 large crystal, 39 subgrain boundary, 40 origin of normal crystal, 41 origin of large crystal, 44 channel region, 45 silicon island region (active layer), 46 gate electrode, 61 source electrode, 62 drain electrode, 63 gate electrode, 64 channel region, 65 silicon island region (active layer), 66 insulating layer, 67 buffer layer (insulating layer), 68 insulating substrate, 200, 202 semiconductor device manufacturing apparatus, C laser light irradiation region.

Claims (14)

A method for manufacturing a semiconductor device comprising a substrate and a crystalline semiconductor film laminated directly or indirectly on the substrate,
Laminating an amorphous semiconductor film directly or indirectly on the substrate;
Forming a first cap film on a part of the surface of the amorphous semiconductor film;
Forming a second cap film on a part of the region where the first cap film is not formed on the surface of the amorphous semiconductor film;
Of the surface of the amorphous semiconductor film, a region including both the first cap film and the second cap film, the first cap film, and the second cap film, Irradiating a laser beam to melt a part of the amorphous semiconductor film in a solid state into a liquid state;
Crystallization of the liquid semiconductor to convert it to the crystalline semiconductor film;
A method for manufacturing a semiconductor device.   The step of melting the amorphous semiconductor film in a liquid state includes the step of forming the first cap film and the second cap film, and the first cap film and the second cap film. A region between which the first cap film and the second cap film are formed, and the first cap film and the first cap film are melted over the thickness of the amorphous semiconductor film. A laser beam having an irradiance and an irradiation time that does not melt the region sandwiched between the two cap films and the region other than the thickness of the amorphous semiconductor film in the surface of the amorphous semiconductor film. The amorphous state in a solid state by irradiating the region including both the one cap film and the second cap film, the first cap film, and the second cap film. semiconductor Comprising the step of melting a part in liquid state, a method of manufacturing a semiconductor device according to claim 1.   The step of converting into the crystalline semiconductor film includes a region including both the first cap film and the second cap film in the surface of the amorphous semiconductor film, the first cap film, 2. The method according to claim 1, further comprising the step of crystallizing the liquid semiconductor and converting it to the crystalline semiconductor film in a state where the second cap film is irradiated with a second laser beam. A method for manufacturing a semiconductor device.   The step of converting into the crystalline semiconductor film includes a region including both the first cap film and the second cap film in the surface of the amorphous semiconductor film, the first cap film, In contrast to the second cap film, in the case of single irradiation, the second laser beam is irradiated under conditions of irradiance and irradiation time that cannot heat the amorphous semiconductor film to a temperature higher than the melting point. 2. The method of manufacturing a semiconductor device according to claim 1, comprising a step of crystallizing the semiconductor in the liquid state and converting it to the crystalline semiconductor film in an irradiated state.   The step of melting the amorphous semiconductor film in a liquid state includes a region including both the first cap film and the second cap film on the surface of the amorphous semiconductor film, and the first By irradiating the cap film and the second cap film with the first laser beam and the second laser beam, a part of the amorphous semiconductor film in a solid state is brought into a liquid state. Including the step of melting, and the step of converting into the crystalline semiconductor film includes the step of crystallizing the liquid state semiconductor and converting it into the crystalline semiconductor film in the state irradiated with the second laser beam. A method for manufacturing a semiconductor device according to claim 1.   The step of melting the amorphous semiconductor film into a liquid state includes a region including both the first cap film and the second cap film, the first cap film, and the second cap film. Are irradiated with a second laser beam having an irradiation region including an irradiation region of the first laser beam and the first laser beam, thereby providing one of the amorphous semiconductor films in a solid state. The method for manufacturing a semiconductor device according to claim 5, comprising a step of melting the part into a liquid state.   The step of forming the first cap film includes the step of forming a first cap film having a reflectance lower than that of the amorphous semiconductor film with respect to the laser light, and the second cap. The step of forming a film includes a reflectance of the amorphous semiconductor film with respect to the laser beam on a part of the region on the surface of the amorphous semiconductor film where the first cap film is not formed. The method for manufacturing a semiconductor device according to claim 1, comprising a step of forming a second cap film having a lower reflectance.   2. The step of forming the second cap film includes the step of forming a second cap film in which at least a part of a boundary surface facing the first cap film is concave. A method for manufacturing a semiconductor device.   The method for manufacturing a semiconductor device according to claim 1, further comprising a step of forming a channel region of a thin film transistor in a region where the first cap film and the second cap film are not formed in the crystalline semiconductor film.   2. The semiconductor device according to claim 1, wherein the step of converting into a crystalline semiconductor film includes the step of crystallizing the liquid semiconductor to convert it into a single crystalline semiconductor film and / or a polycrystalline semiconductor film. Production method.   The step of laminating the amorphous semiconductor film is performed directly or indirectly on the substrate from a polycrystalline semiconductor film, a microcrystalline semiconductor film, and an amorphous semiconductor film having lower crystallinity than the crystalline semiconductor film. The manufacturing method of the semiconductor device of Claim 1 including the process of laminating | stacking 1 or more types chosen from consisting of.   The semiconductor device manufacturing method according to claim 1, wherein the step of laminating the amorphous semiconductor film includes a step of laminating an amorphous semiconductor film containing a silicon-based semiconductor as a material directly or indirectly on the substrate. Method.   The step of forming the first cap film includes a step of forming a first cap film containing silicon dioxide as a material, and the step of forming the second cap film includes a surface of the amorphous semiconductor film. 2. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of forming a second cap film containing silicon dioxide as a material on a part of the upper region where the first cap film is not formed.   The step of forming the second cap film includes the step of forming the first cap film and the second cap over a portion of the surface of the amorphous semiconductor film where the first cap film is not formed. The method for manufacturing a semiconductor device according to claim 1, comprising a step of forming a second cap film at a position where the shortest distance to the cap film is equal to or longer than the width of the channel region of the thin film transistor.

Images