JP3859744B2 - Method for manufacturing semiconductor device and active matrix display device - Google Patents

Description

[0001]
[Industrial application fields]
The invention disclosed in this specification relates to a method for manufacturing a thin film semiconductor formed over a substrate having an insulating surface such as a glass substrate.
[0002]
[Prior art]
In recent years, thin film transistors have attracted attention as semiconductor devices using thin film semiconductors. In particular, a configuration in which a thin film transistor is mounted on a liquid crystal electro-optical device has attracted attention. In this method, a thin film semiconductor is formed on a glass substrate constituting a liquid crystal electro-optical device, and a thin film transistor is formed using the thin film semiconductor. In this case, the thin film transistor is disposed on each pixel electrode of the liquid crystal electro-optical device, and has a function as a switching element that controls electric charges entering and exiting the pixel electrode. Such a structure is called an active matrix type liquid crystal display device and can display a very high quality image.
[0003]
As a thin film semiconductor used for the thin film transistor, an amorphous silicon thin film is mainly used. However, in the present situation, the required characteristics cannot be obtained with an amorphous silicon thin film.
[0004]
In order to improve the characteristics of the amorphous silicon film, it is useful to crystallize the amorphous silicon film to form a crystalline silicon film. As a method for obtaining a crystalline silicon film, a method is known in which an amorphous silicon film is formed by a plasma CVD method or a low pressure thermal CVD method and then subjected to heat treatment.
[0005]
On the other hand, when a thin film transistor is used in an active matrix type liquid crystal electro-optical device, there is a problem in that it is necessary to use a glass substrate as a substrate from the viewpoint of economy.
[0006]
In order to crystallize the amorphous silicon film by heating, heat treatment must be performed at a temperature of 600 ° C. or more for several tens of hours or more. On the other hand, a glass substrate warps or deforms when heating at 600 ° C. or more is applied for several tens of hours or more. This becomes particularly remarkable when the glass substrate has a large area. Since the liquid crystal electro-optical device needs to have a configuration in which a liquid crystal is sandwiched and held between glass substrates laminated with an interval of several μm, deformation of the glass substrate causes display unevenness and the like, which is not preferable.
[0007]
In order to avoid this problem, a quartz substrate or a special glass substrate that can withstand high-temperature heat treatment may be used as the substrate. However, quartz substrates and special glass substrates that can withstand high temperatures are expensive and difficult to use in terms of production costs.
[0008]
A technique for crystallizing an amorphous silicon film by laser light irradiation is also known. When laser light irradiation is used, a crystalline silicon film having very good local crystallinity can be obtained. On the other hand, the uniformity of the effect of laser light irradiation is difficult to obtain over the entire film. Further, the obtained crystalline silicon film also has a problem that there are many variations in each process (in other words, reproducibility is low).
[0009]
[Problems to be solved by the invention]
An object of the invention disclosed in this specification is to provide a method for obtaining a crystalline silicon film having good crystallinity. In particular, when a glass substrate is used as a substrate, it is an object to obtain a crystalline silicon film having good crystallinity.
[0010]
[Means for Solving the Problems]
One of the inventions disclosed in this specification is:
Forming an amorphous silicon film over a substrate having an insulating surface;
Before or after the step, contacting and holding a metal element that promotes crystallization of silicon on the back surface or the surface of the amorphous silicon film;
Irradiating the amorphous silicon film with microwaves, selectively heating the surface of the amorphous silicon film due to the skin effect and transforming it to a crystalline silicon film;
It is characterized by having.
[0011]
In the above structure, a glass substrate can be typically given as a substrate having an insulating surface. The invention disclosed in this specification is useful when a glass substrate that is vulnerable to heating is used. In addition to the glass substrate, a quartz substrate or a semiconductor substrate on which an insulating film is formed can be used.
[0012]
As the amorphous silicon film, a film formed by a plasma CVD method or a low pressure thermal CVD method can be used. In particular, a silicon film formed by a low pressure thermal CVD method is convenient because the amount of hydrogen in the film is small and the film can be easily crystallized.
[0013]
As the metal element that promotes crystallization of silicon, one or more kinds of elements selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au can be used.
[0014]
Among the metal elements, it is particularly useful to use Ni (nickel). Ni has been experimentally obtained with extremely high reproducibility of its effects.
[0015]
In order to introduce the metal element, it is preferable to use a method of applying a solution containing the metal element. If the metal element is held in contact with the back surface of the amorphous silicon film, the metal element is held in contact with the surface to be formed before the amorphous silicon film is formed. If the metal element is held on the surface of the amorphous silicon film, the metal element may be held in contact with the amorphous silicon film after the film formation. Further, these metal elements are finally contained in the raw film at 1 × 10 ¹⁶ ~ 1x10 ¹⁹ Atom cm ^-3 It is important to devise it so that it is contained at a concentration of. The concentration of this metal element is defined as the minimum value obtained by SIMS (secondary ion analysis method).
[0016]
The case where a metal element is introduced using a solution will be described below. For example, when Ni is used as a metal element, nickel compounds such as nickel bromide, nickel acetate, nickel oxalate, nickel carbonate, nickel chloride, nickel iodide, nickel nitrate, nickel sulfate, nickel formate, nickel acetylacetonate And at least one selected from nickel 4-cyclohexylbutyrate, nickel oxide, nickel hydroxide, and nickel 2-ethylhexanoate. That is, nickel element can be introduced by applying these solutions on the surface where the amorphous silicon film is formed or on the amorphous silicon film.
[0017]
Moreover, you may use what contained Ni in the nonpolar solvent which is benzene, toluene, xylene, carbon tetrachloride, chloroform, ether, trichloroethylene, and Freon.
[0018]
When Fe (iron) is used as the metal element, a material known as an iron salt, such as ferrous bromide (FeBr) ₂ 6H ₂ O), ferric bromide (FeBr) _Three 6H ₂ O), ferric acetate (Fe (C ₂ H _Three O ₂ ) _Three xH ₂ O), ferrous chloride (FeCl ₂ 4H ₂ O), ferric chloride (FeCl _Three 6H ₂ O), ferric fluoride (FeF) _Three 3H ₂ O), ferric nitrate (Fe (NO _Three ) _Three 9H ₂ O), ferrous phosphate (Fe _Three (PO _Four ) ₂ 8H ₂ O), ferric phosphate (FePO _Four 2H ₂ Those selected from O) can be used.
[0019]
When Co (cobalt) is used as the metal element, a material known as a cobalt salt, such as cobalt bromide (CoBr6H) ₂ O), cobalt acetate (Co (C ₂ H _Three O ₂ ) ₂ 4H ₂ O), cobalt chloride (CoCl ₂ 6H ₂ O), cobalt fluoride (CoF) ₂ xH ₂ O), cobalt nitrate (Co (No _Three ) ₂ 6H ₂ Those selected from O) can be used.
[0020]
When Ru (ruthenium) is used as the metal element, a material known as a ruthenium salt, such as ruthenium chloride (RuCl), is used. _Three H ₂ O) can be used.
[0021]
When Rh (rhodium) is used as a metal element, a material known as a rhodium salt, such as rhodium chloride (RhCl), is used. _Three 3H ₂ O) can be used.
[0022]
When Pd (palladium) is used as the metal element, a material known as a palladium salt, such as palladium chloride (PdCl ₂ 2H ₂ O) can be used.
[0023]
When Os (osnium) is used as the metal element, a material known as an osnium salt, for example, osmium chloride (OsCl) _Three ) Can be used.
[0024]
When Ir (iridium) is used as the metal element, a material known as an iridium salt, such as iridium trichloride (IrCl _Three 3H ₂ O), iridium tetrachloride (IrCl _Four ) Can be used.
[0025]
When Pt (platinum) is used as the metal element, a material known as a platinum salt as the compound, for example, platinous chloride (PtCl) is used. _Four 5H ₂ O) can be used.
[0026]
When Cu (copper) is used as the metal element, cupric acetate (Cu (CH _Three COO) ₂ ), Cupric chloride (CuCl ₂ 2H ₂ O), cupric nitrate (Cu (NO _Three ) ₂ 3H ₂ Materials selected from O) can be used.
[0027]
When gold is used as the metal element, gold trichloride (AuCl _Three xH ₂ O), gold chloride (AuHCl) _Four 4H ₂ Materials selected from O) can be used.
[0028]
A method using such a solution is very useful for uniform crystallization because the metal element can be dispersed and held in contact with the amorphous silicon film. Further, it is useful because the concentration can be easily controlled.
[0029]
It is appropriate to use a microwave having a frequency of 1 to 10 GHz. By irradiating the amorphous silicon film with microwaves, the amorphous silicon film can be transformed into a crystalline silicon film because the microwave is absorbed by the bond between silicon and hydrogen (Si-H bond) As a result, the amorphous silicon film is heated. Further, when a glass substrate is used, the microwave is absorbed by the surface of the amorphous silicon film due to the skin effect, so that the glass substrate is not directly heated. This is useful when using a glass substrate that is vulnerable to heating.
[0030]
In addition, when an amorphous silicon film formed on a glass substrate is heated by irradiation with microwaves from the surface side of the amorphous silicon film, crystal growth proceeds from the surface of the film. Growth can be done.
[0031]
FIG. 9 shows that a silicon oxide film 902 as a base film is formed on a glass substrate 901, and further an amorphous silicon film 903 is formed by a plasma CVD method or a low pressure thermal CVD method, and further heated by a heater. It is the schematic which showed the state which crystallizes the amorphous silicon film 903.
[0032]
In such a case, there is thermal conduction from the side of the glass substrate 901 having a large heat capacity, and there are defects and stress that become nuclei during crystallization at the interface between the silicon oxide film 902 and the amorphous silicon film 903 as the base film. For example, crystal growth proceeds from the substrate side as indicated by an arrow 904. At this time, since the portion that becomes the nucleus of crystal growth exists non-uniformly, the crystal growth also becomes non-uniform.
[0033]
On the other hand, FIG. 10 shows that a silicon oxide film 902 as a base film is formed on a glass substrate 901, and further an amorphous silicon film 903 is formed by a plasma CVD method or a low pressure thermal CVD method. It is the schematic which showed the state which crystallizes the amorphous silicon film 903 by irradiation of the shown microwave.
[0034]
In this case, since the microwave 906 is selectively absorbed by the surface of the amorphous silicon film 903, the heating is selectively performed from the surface of the amorphous silicon film 903. Crystal growth also proceeds from the surface of the amorphous silicon film as indicated by 905. Unlike the case shown in FIG. 9, this crystallization step is not affected by the interface with the base or the substrate, and therefore uniform crystal growth can be achieved.
[0035]
Other aspects of the invention are:
Forming an amorphous silicon film over a substrate having an insulating surface;
Before or after the step, contacting and holding a metal element that promotes crystallization of silicon on the back surface or the surface of the amorphous silicon film;
Transforming the amorphous silicon film into a crystalline silicon film by irradiating the amorphous silicon film with microwaves in a high vacuum atmosphere;
It is characterized by having.
[0036]
The high vacuum state in the above configuration means a state in which the degree of vacuum is kept as high as possible. This state differs depending on the performance and maintenance state of the exhaust pump to be used and the vacuum chamber to be used. However, it is important to make the degree of vacuum as high as possible.
[0037]
The reason why the degree of vacuum is as high as possible is to prevent generation of plasma by microwave irradiation. When plasma is generated, the film is etched by ions and active species in the plasma, and defects are formed in the film, which is inconvenient for obtaining a good quality crystalline silicon film.
[0038]
Other aspects of the invention are:
Forming an amorphous silicon film over a substrate having an insulating surface;
Before or after the step, contacting and holding a metal element that promotes crystallization of silicon on the back surface or the surface of the amorphous silicon film;
Transforming the amorphous silicon film to a crystalline silicon film by irradiating the amorphous silicon film with microwaves in an atmosphere that does not generate plasma;
It is characterized by having.
[0039]
As an atmosphere in which plasma is not generated, a high vacuum state can be used as much as possible. (Plasma is generated by applying high power unless it is the most complete high vacuum)
[0040]
Air or the like can be said to be an atmosphere in which plasma is hardly generated. However, the fact that plasma is not generated is a problem that varies depending on the frequency and power of the input microwave. Therefore, here, the definition that the state in which plasma is not generated is a state in which light emission of plasma cannot be visually confirmed is adopted.
[0041]
[Action]
The amorphous silicon film formed by a vapor phase method can be crystallized by heating in high vacuum by microwave irradiation. Microwaves are easily absorbed by the bond between silicon and hydrogen, and are selectively absorbed by an amorphous silicon film essentially containing a large amount of hydrogen. In particular, microwaves are selectively absorbed on the surface of the amorphous silicon film by the skin effect. The amorphous silicon film is selectively heated from the surface. The energy of this heating promotes the detachment of hydrogen molecules from the film, and the rate of bonding between silicon molecules increases. Then, the amorphous silicon film can be transformed into a crystalline silicon film. In addition, by using a metal element that promotes crystallization of silicon, reproducibility of the crystallization process can be increased. In addition, high crystallinity can be obtained by using a metal element that promotes crystallization of silicon.
[0042]
In addition, when heat treatment is performed on the amorphous silicon film in advance to release hydrogen from the film, crystallization by microwave irradiation can be performed with higher reproducibility. Moreover, higher crystallinity can be obtained. Further, after the microwave irradiation, further heating or laser light irradiation is effective in improving reproducibility of obtaining a crystalline silicon film (stability for obtaining a predetermined film quality).
[0043]
【Example】
[Example 1]
This embodiment relates to a structure in which a crystalline silicon film is formed on a glass substrate. First, a silicon oxide film is formed as a base film on a glass substrate. This silicon oxide film functions to prevent diffusion of impurities from the glass substrate. It also functions to relieve stress generated between the glass substrate and the semiconductor film. This silicon oxide film may be formed to a thickness of about 3000 mm by plasma CVD or sputtering.
[0044]
Next, an amorphous silicon film is formed. The amorphous silicon film may be formed by a plasma CVD method or a low pressure thermal CVD method. The thickness of the amorphous silicon film may be a required thickness, but is 500 mm here.
[0045]
When the amorphous silicon film is formed, a nickel acetate solution whose concentration is controlled to a predetermined nickel concentration is applied by spin coating. Then, 2.45 GHz microwave is irradiated to heat the amorphous silicon film.
[0046]
FIG. 1 shows an outline of an apparatus for performing microwave irradiation on an amorphous silicon film. The apparatus shown in FIG. 1 irradiates a glass substrate 107 formed with an amorphous silicon film disposed on a substrate holder 106 with a 2.45 GHz microwave (output 5 kW) generated by an oscillator 104. This is a device for crystallizing an amorphous silicon film on 107.
[0047]
In order to perform processing by microwave irradiation, the substrate 107 is first placed in the vacuum chamber 103. The substrate 107 is disposed on the substrate holder 106. The substrate holder 106 can be moved back and forth by the adjustment rod 108. This is because the position of the substrate is important depending on the state of the standing wave generated in the chamber. In this embodiment, the substrate 107 is arranged in a region where the microwave electric field strength is maximum.
[0048]
After the substrate 107 is disposed, the chamber is closed and the inside is purged with nitrogen gas. Then, a high vacuum state is set using the exhaust pump 105. As the exhaust pump, it is desirable to use a high-vacuum pump such as a turbo molecular pump. In addition, depending on the type of turbo molecular pump, there are those that can be destroyed when used at normal pressure. In that case, a rotary pump may be used in combination.
[0049]
As the high vacuum state here, it is necessary to have a degree of vacuum that does not generate plasma by microwaves.
[0050]
When the inside of the chamber 103 is brought into a high vacuum state by the exhaust pump 105, a microwave of 2.45 GHz is oscillated from the microwave oscillator 104. The microwave is supplied into the chamber 103 via the waveguide 102. Then, the microwave is irradiated to the amorphous silicon film on the substrate 107, and the film is crystallized.
[0051]
A heater is built in the substrate holder 106, and the substrate can be heated to a predetermined temperature. Here, the substrate is heated at a temperature of 550 ° C. When using a glass substrate, it is desirable to select a temperature as high as possible below the strain point. In general, a temperature from 400 ° C. to a temperature below the strain point of the glass substrate may be selected. When a glass substrate is not used as the substrate, the upper limit of the heating temperature may be determined in view of the heat resistance of the substrate.
[0052]
In general, since temperature measurement during heating is performed on the back side of the glass substrate, it is difficult to accurately measure the temperature of the silicon film on the glass substrate. In that case, the temperature on the back side of the glass substrate may be used as the heating temperature.
[0053]
After the amorphous silicon film is crystallized by irradiating the amorphous silicon film with microwaves, the substrate is taken out of the apparatus and the crystallization process is completed.
[0054]
[Example 2]
This embodiment relates to a configuration in which heating is further performed on a silicon film crystallized by microwave irradiation. The reason for further heating is to obtain a margin for the crystallization process. That is, to obtain a crystalline silicon film with higher reproducibility.
[0055]
The heating performed here is preferably performed at a temperature of 400 ° C. to a strain point of the glass substrate or lower with respect to the silicon film that has been crystallized by the microwave irradiation. In general, the heat treatment may be performed at a temperature of 400 ° C. to 600 ° C. for about 1 to 4 hours. As a heating method, a method using heating with a heater or irradiation with an infrared lamp may be adopted.
[0056]
When heating is performed, defects in the film can be reduced. In addition, the crystallinity of the film can be improved. In general, there is no variation between steps, and a crystalline silicon film having a certain film quality can be obtained.
[0057]
Example 3
This embodiment relates to a configuration in which a silicon film crystallized by microwave irradiation is further irradiated with a laser beam to improve crystallinity and a margin in a crystallization process.
[0058]
In general, when a method of obtaining a crystalline silicon film by irradiating an amorphous silicon film with laser light, as described above, the uniformity of the quality of the obtained crystalline silicon film and variations in process results Problems arise.
[0059]
However, as shown in this example, when further irradiating a laser beam to a silicon film crystallized once, an effect of improving crystallinity is obtained, and the effect is obtained with high reproducibility. Can do.
[0060]
When the amorphous silicon film is suddenly irradiated with laser light, a sudden phase change from the amorphous state to the crystalline state occurs. And due to this sudden phase change, the reproducibility of the obtained crystal state becomes unstable.
[0061]
However, when a laser beam is irradiated onto a silicon film that has been crystallized once by heating by microwave irradiation, a rapid phase change does not occur, and the effect can be made constant. That is, reproducibility of the effect of laser light irradiation can be ensured.
[0062]
In addition, it is effective to heat the surface to be irradiated at the time of laser light irradiation. This heating temperature is preferably performed at a temperature of 400 ° C to 600 ° C. This has the effect of reducing the impact of energy upon laser light irradiation and suppressing the formation of a clear crystal grain boundary and the roughness of the film surface. Moreover, it can prevent that a defect arises in a film | membrane.
[0063]
Example 4
The present embodiment relates to a configuration in which after crystallization of an amorphous silicon film by microwave irradiation, crystallization is further improved by laser light irradiation, and annealing by heating is further performed. Irradiation with laser light has the effect of crystallizing the amorphous component remaining in the silicon film and improving the crystallinity of the film. Also, annealing by heating has the effect of reducing film defects.
[0064]
Employing such a configuration has a demerit that the number of processes increases, but the reproducibility of the quality of the obtained crystalline silicon film can be very high.
[0065]
Alternatively, a configuration may be adopted in which laser light irradiation is performed after heating, and further heating is performed. Furthermore, laser light irradiation and heating may be alternately repeated a plurality of times. By doing so, the reproducibility of the crystallinity and the electrical property of the obtained crystalline silicon film can be enhanced. However, since the number of processes increases, there is a disadvantage that productivity is lowered.
[0066]
Example 5
This embodiment shows an example in which a thin film transistor is manufactured using a crystalline silicon film manufactured using the invention disclosed in this specification. FIG. 2 shows a manufacturing process of the thin film transistor shown in this embodiment. First, a silicon oxide film 202 functioning as a base film is formed on the glass substrate 201 by sputtering to a thickness of 3000 mm. Next, an amorphous silicon film 203 is formed to a thickness of 500 mm by plasma CVD or low pressure thermal CVD. (Fig. 2 (A))
[0067]
A metal element that promotes crystallization of silicon is held in contact with the amorphous silicon film. Here, a nickel acetate solution adjusted to a predetermined concentration is applied using a spinner so that a metal element that promotes crystallization of silicon is held in contact with the amorphous silicon film.
[0068]
Next, microwave irradiation is performed on the amorphous silicon film. Here, the amorphous silicon film 203 is irradiated with microwaves using the apparatus shown in FIG. 1 to transform the amorphous silicon film 203 into a crystalline silicon film. At this time, the surface to be formed is heated to a temperature of 550 ° C. Microwave irradiation is performed in a high vacuum.
[0069]
Note that the position of the substrate is adjusted by operating the adjustment rod 108 (see FIG. 1), and the position of the substrate is adjusted to a region where the electric field intensity is maximum.
[0070]
After the amorphous silicon film 203 is crystallized by microwave irradiation, laser light irradiation is performed to improve its crystallinity. Here, a KrF excimer laser is used. This laser beam is formed into a linear beam having a width of 5 mm and a length of 20 cm, and its energy density is 350 mJ / cm. ² And In the laser light irradiation step, the surface to be formed is heated to 550 ° C.
[0071]
Thus, the amorphous silicon film 203 is transformed into a crystalline silicon film. Next, by patterning, an active layer 204 of the thin film transistor is formed as shown in FIG.
[0072]
Next, a silicon oxide film 205 functioning as a gate insulating film is formed to a thickness of 1000 mm by plasma CVD or sputtering. Further, a film mainly composed of aluminum for constituting the gate electrode is formed to a thickness of 6000 mm. As a film formation method, a sputtering method or an electron beam evaporation method may be used. Then, the gate electrode 206 is formed by patterning. Further, anodic oxidation is performed in the electrolytic solution using the gate electrode 206 as an anode, thereby forming an anodic oxide layer 207 around the gate electrode. The thickness of the anodic oxide layer is 2000 mm. In this way, the state shown in FIG.
[0073]
Next, impurity ions for forming source / drain regions are accelerated and implanted by ion implantation or plasma doping. In this step, impurity ions are implanted into the regions 208 and 211 by using the gate electrode 206 and the surrounding anodic oxide layer 207 as a mask. Here, P (phosphorus) ions are implanted in order to manufacture an N-channel thin film transistor. In the region 209, impurity ions are not implanted by using the anodic oxide layer 207 as a mask. Further, since the gate electrode 206 serves as a mask in the region 210, impurity ions are not implanted.
[0074]
After the impurity ions are implanted, laser light irradiation is performed to activate the implanted impurity ions and anneal the region into which the impurity ions are implanted. Thus, the source region 208 and the drain region 211 are formed in a self-aligning manner. At the same time, the region 209 can be formed as an offset gate region, and the region 210 can be formed as a channel formation region. (Fig. 2 (C))
[0075]
Next, a silicon oxide film 212 having a thickness of 6000 mm is formed as an interlayer insulating film. This silicon oxide film 212 is formed by plasma CVD. Next, contact holes are formed, and a source electrode 213 and a drain electrode 214 are formed. Then, heat treatment is further performed in a hydrogen atmosphere at 350 ° C. for 1 hour, whereby the thin film transistor illustrated in FIG. 2D is completed.
[0076]
Example 6
The manufacturing process of this example is shown in FIG. This embodiment is characterized in that, in the manufacturing process of the thin film transistor shown in FIG. 2, crystallization is performed by microwave irradiation after patterning the amorphous silicon film. That is, after forming a pattern constituting the active layer (this pattern is amorphous), micro irradiation is performed to crystallize this pattern.
[0077]
Note that in the structure shown in this example, the manufacturing conditions and the like are the same as in Example 4 unless otherwise specified.
[0078]
First, as shown in FIG. 3A, a silicon oxide film 202 is formed as a base film over a glass substrate 201. Next, an amorphous silicon film (not shown) is formed on the silicon oxide film 202. Then, by patterning, a region 204 to be an active layer of the thin film transistor is formed. Here, the region to be the active layer is in an amorphous state. (Fig. 3 (A))
[0079]
In this state, a nickel acetate solution adjusted to a predetermined concentration is applied by spin coating. Then, using the apparatus shown in FIG. 1, microwave irradiation is performed on the patterned amorphous silicon pattern. In such a configuration, crystallization is performed on a small region of several tens of μm square or less by microwave irradiation, so that the crystallinity can be further increased.
[0080]
Thus, when the state shown in FIG. 3A is obtained, a thin film transistor is completed according to the same steps as those shown in FIG. That is, the process illustrated in FIG. 3B is the same as the process illustrated in FIG. Further, the step shown in FIG. 3C is the same as the step shown in FIG. Further, the process illustrated in FIG. 3D is the same as the process illustrated in FIG.
[0081]
When the structure shown in this embodiment is adopted, the crystallinity of the side surface of the active layer can be improved. If the crystallinity of the side surface of the active layer can be improved, the density of trap levels on the side surface of the active layer can be reduced. When trap levels exist at a high density on the side surface of the active layer, an OFF current caused by carrier movement via the trap level on the side surface of the active layer becomes a problem when the transistor is turned off. Therefore, as shown in this embodiment, the OFF current can be reduced by improving the crystallinity of the side surface of the active layer and lowering the density of trap levels there.
[0082]
Example 7
This embodiment relates to a structure in which a mask is provided over an amorphous silicon film and microwave irradiation is performed. In this embodiment, the mask is provided in order to selectively irradiate microwaves and selectively perform crystallization.
[0083]
FIG. 4 shows an outline of an active matrix type liquid crystal display device incorporating a peripheral drive circuit. That is, FIG. 4 shows a configuration in which a pixel region and a peripheral driver circuit for driving a thin film transistor arranged in the pixel region are integrated on the same glass substrate. FIG. 4 shows a single glass substrate. When a liquid crystal cell is formed, an opposing glass substrate is prepared, and the glass substrate and the glass substrate shown in FIG. The liquid crystal is held.
[0084]
In the configuration shown in FIG. 4, a pixel region 402 in which pixel electrodes are arranged in a matrix of several hundreds × several hundreds on a glass substrate 401, a peripheral drive circuit 403 for driving thin film transistors arranged in the pixel region 402, 404 is arranged. The peripheral drive circuit and the pixel region are connected by wiring patterns 405 and 406.
[0085]
At least one thin film transistor is disposed in one of the pixels constituting the pixel region 402. The peripheral drive circuits 403 and 404 are constituted by a shift register circuit, an analog buffer circuit, or the like.
[0086]
In the configuration as shown in FIG. 4, required characteristics are different between the thin film transistors arranged in the pixel region 402 and the thin film transistors arranged in the peripheral driver circuits 403 and 404.
[0087]
The thin film transistor disposed in the pixel region 402 is not required to have high mobility, but is required to have low OFF current characteristics. Note that if a thin film transistor disposed in the pixel region is formed using a semiconductor film having high mobility, it may cause malfunction or malfunction due to light irradiation, and thus mobility greater than necessary is unnecessary.
[0088]
On the other hand, the thin film transistors arranged in the peripheral driver circuits 403 and 404 are required to operate at high speed and to pass a large current, and therefore have high mobility.
[0089]
As described above, it is necessary to separately form thin film transistor groups having different characteristics on one glass substrate.
[0090]
In this embodiment, in order to form a thin film transistor having different characteristics as described above on a single glass substrate, the amorphous silicon film is selectively irradiated with microwaves, thereby selectively crystallizing. Regions with different properties are formed. A specific manufacturing process is shown below.
[0091]
First, a silicon oxide film (not shown) is formed on the glass substrate 401 as a base film. Then, an amorphous silicon film serving as a starting film for forming the active layer of the thin film transistor is formed. Here, a metallic mask is arranged so that the microwave hits only the regions 407 and 408 in FIG. Then, a 2.45 GHz microwave (output 5 kW) is irradiated using the apparatus shown in FIG.
[0092]
When the microwave is irradiated in a state where the mask is arranged, the microwave is irradiated only in the regions 407 and 408. Only this region is crystallized. On the other hand, in this state, other regions remain in an amorphous state.
[0093]
Then, the mask is removed and heat treatment is performed at a temperature of 550 ° C. for 2 hours. Through these steps, the silicon film in the region constituting the peripheral driver circuit 404 can be a crystalline silicon film, and at the same time, the silicon film constituting the thin film transistor in the pixel region 402 can be an amorphous silicon film.
[0094]
The peripheral driver circuit can be formed using a thin film transistor using a crystalline silicon film having high mobility. The thin film transistor disposed in the pixel region is formed of an amorphous silicon film having low mobility but low OFF current. The thin film transistor used can be obtained.
[0095]
Example 8
The present embodiment is characterized in that the amorphous silicon film is selectively irradiated with microwaves having different intensities by selectively attenuating the microwaves to selectively vary the crystallinity.
[0096]
In general, quartz glass transmits almost all microwaves. On the other hand, the amorphous silicon film absorbs microwaves. Therefore, by selecting the film thickness of the amorphous silicon film as appropriate, it is possible to irradiate microwaves with weaker power in the region provided with the mask than in other regions.
[0097]
Here, the substrate shown in FIG. 4 is irradiated with weak microwaves in the region of the pixel region 402. That is, quartz glass having a thin amorphous silicon film (for example, having a thickness of 500 mm) is prepared in a region corresponding to the region 402, and the quartz glass is overlaid on the glass substrate 401. In this state, microwave irradiation is performed.
[0098]
FIG. 5 schematically shows a state in which microwaves pass through the quartz glass on which the amorphous silicon film is selectively formed. In FIG. 5, 51 is a quartz substrate. Reference numeral 52 denotes an amorphous silicon film formed on a quartz substrate. FIG. 5 shows a mask that partially attenuates the microwave.
[0099]
When the microwave 53 is transmitted through the quartz substrate, the microwave is absorbed at a predetermined rate in the amorphous silicon film 52. Therefore, the energy of the microwave 55 transmitted through this region is transferred to the microwave 54 in another region. It can be weakened in comparison. Adjustment of the attenuation of the microwave can be realized by controlling the film thickness of the amorphous silicon film 52.
[0100]
The region of the pixel region 402 is irradiated with microwaves through a mask made of quartz glass in which an amorphous silicon film is formed in a region corresponding to the region 402 in FIG. Power can be weakened compared to other areas. Accordingly, the crystallinity of the pixel region 408 can be lower than that of other regions.
[0101]
If the crystallinity is poor, the mobility becomes small. In addition, the resistance is increased, and the value of the OFF current is reduced accordingly. If the crystallinity is high, a silicon film with high mobility can be obtained.
[0102]
In this manner, the thin film transistor disposed in the pixel region 402 can be configured with a small mobility but a small OFF current value. The thin film transistors disposed in the peripheral driver circuits 403 and 404 can be thin film transistors having high mobility.
[0103]
Example 9
FIG. 6 shows an apparatus shown in this embodiment. The apparatus shown in FIG. 6 is characterized in that the following steps are performed in a continuously controlled atmosphere. That is, first, a step of preheating a substrate on which an amorphous silicon film is formed (a glass substrate is generally used), and then a step of crystallizing the amorphous silicon film by microwave irradiation, Further, the heat treatment is further performed, and the step of obtaining the crystalline silicon film is performed in a continuously controlled atmosphere (including a high vacuum state).
[0104]
The apparatus shown in FIG. 6 is formed on a substrate, a substrate loading / unloading chamber 501 for loading / unloading the substrate into / from the apparatus, a processing chamber 502 for irradiating the amorphous silicon film formed on the substrate with microwaves, and the substrate. A heating chamber 503 for heating the silicon film, and a substrate transfer chamber 505 having means for transferring the substrate between the chambers.
[0105]
FIG. 7 is a cross section taken along line AA ′ in FIG. Further, FIG. 8 shows a cross section taken along line BB ′ in FIG. Each chamber has a structure in which airtightness is maintained, and can have a high vacuum state as necessary. The chambers are connected to each other through gate valves indicated by substrate transfer chambers 505 and 506, 507, and 508, which are common chambers. The gate valve has a structure that can maintain sufficient airtightness.
[0106]
Next, each room will be described in detail. Reference numeral 501 denotes a substrate loading / unloading chamber for loading / unloading the substrate into / from the apparatus. As shown in FIG. 8, the cassette 511 is loaded into the chamber from the outside of the apparatus through the door 514 in a state where a large number of substrates 511 are stored in the cassette 510. Further, after the processing is completed, the substrate is carried out from the door 514 to the outside of the apparatus for each cassette 510.
[0107]
The substrate loading / unloading chamber 501 is provided with a purge gas introduction system 512 such as an inert gas, an unnecessary gas exhaust, and an exhaust pump 513 for reducing the pressure in the chamber to a high vacuum state. The purge gas here is used to clean the room by filling the room with a clean gas at one end.
[0108]
Reference numeral 502 in FIGS. 6 and 7 denotes a processing chamber for irradiating the amorphous silicon film formed on the substrate with microwaves. The microwave is oscillated by an oscillator 516 and introduced into the processing chamber 502 through a waveguide 517. Then, a crystallization process is performed on the sample placed on the substrate stage 515 with this microwave. In addition, the height of the substrate stage 515 can be adjusted.
[0109]
Further, the processing chamber 502 has an exhaust system including a gas introduction system (not shown) and an exhaust pump 504. From the gas introduction system, an inert gas for purging or a gas (for example, air) that is difficult to generate plasma is supplied.
[0110]
A chamber indicated by 503 in FIGS. 6 and 8 is a chamber (heating chamber) for heating the silicon film. A substrate 511 on which a silicon film is formed is stored on a stage 518 in which a large number of substrates are moved up and down. The substrate stored on the stage 518 is heated by the heater 521 in the heating chamber 503.
[0111]
The heating chamber 503 is also provided with an inert gas introduction system 519 for purging and an exhaust pump 520 that can bring the heating chamber into a high vacuum state.
[0112]
A substrate transfer chamber 505 is a chamber having a function of transferring (transferring) the substrate 511 by the robot arm 522. This chamber is also provided with an inert gas introduction system 523 for purging and an exhaust pump 524 for creating a high vacuum in the chamber. In addition, a heater is built in a part of the hand that holds the substrate of the robot arm 522 so that the temperature of the substrate to be transferred does not change.
[0113]
In actual operation, it is important that the inside of the transfer chamber 505 be in a high vacuum state when the substrate (sample) is transferred.
[0114]
Examples of the operation of the apparatus shown in FIGS. First, a large number of glass substrates 511 to be processed are stored in the cassette 510. In a high vacuum state, the substrates are transferred one by one by the robot arm 522 and carried into the heating chamber 503. In the heating chamber 503, heating is performed at a temperature of 550 ° C. By this heating, the detachment of hydrogen from the film is promoted, and it is possible to make it easy to crystallize. The heating atmosphere is preferably a high vacuum state. Further, if not in a high vacuum state, an inert atmosphere is preferable.
[0115]
After heating in the heating chamber 503 for a predetermined time (for example, 1 hour), the substrate is taken out by the robot arm 522 and transferred to the chamber 502 where microwave irradiation is performed. In this chamber 502, the amorphous silicon film on the glass substrate that has been subjected to the heat treatment is irradiated with microwaves to crystallize the film. Note that microwave irradiation is preferably performed in a high vacuum state. When it is difficult to perform in a high vacuum state, it is necessary to select the frequency and power of the microwave and the atmosphere so that the light emission is not visually observed.
[0116]
When crystallization of the amorphous silicon film by microwave irradiation is completed, the substrate is transferred to the heating chamber 503 by the robot arm. Here, heat treatment after crystallization is performed. Then, after the processing for a predetermined time (for example, 2 hours) is completed, the substrate is transferred to the cassette in the loading / unloading chamber 501. In this way, a series of operation | movement is complete | finished.
[0117]
In the above operation example, the amorphous silicon film is heated at 550 ° C. for 2 hours, and is crystallized by microwave irradiation, and further the annealing at 550 ° C. for 2 hours is controlled on the crystallized silicon film. (Preferably in high vacuum). Note that the gate valve is opened and closed each time the substrate is transported. This is to prevent the influence of heat from the heating chamber 503 and the influence of microwaves from the chamber 502 from reaching other chambers.
[0118]
When an apparatus as shown in this embodiment is used, processing can be performed continuously, so that productivity can be increased. Moreover, high reproducibility can be obtained by controlling the atmosphere.
[0119]
【The invention's effect】
By irradiating the amorphous silicon film with microwaves, the amorphous silicon film can be transformed into a crystalline silicon film. Further, by combining this technique with laser light irradiation and heating steps, a crystalline silicon film can be obtained with high reproducibility.
[0120]
In addition, the crystallization of the amorphous silicon film by microwave irradiation can selectively heat the silicon film, so that the glass substrate is thermally damaged even when the glass substrate is used as the substrate. A crystalline silicon film can be obtained on the glass substrate without any problem.
[Brief description of the drawings]
FIG. 1 shows an outline of an apparatus for irradiating microwaves.
FIG. 2 illustrates a manufacturing process of a thin film transistor.
FIG. 3 illustrates a manufacturing process of a thin film transistor.
FIG. 4 shows a structure of a substrate constituting an active matrix liquid crystal display device.
The
FIG. 5 shows the configuration of a mask that partially attenuates microwaves.
FIG. 6 shows an outline of an apparatus that performs microwave irradiation.
FIG. 7 shows an outline of an apparatus for performing microwave irradiation.
FIG. 8 shows an outline of an apparatus that performs microwave irradiation.
FIG. 9 shows crystallization by microwave irradiation.
FIG. 10 shows a state of crystallization by microwave irradiation.
[Explanation of symbols]
101 Gas supply system
102 Waveguide
103 chamber
104 Microwave generator
105 Exhaust pump
106 Substrate holder
107 Substrate (sample)
108 Operation rod for moving board
201 glass substrate
202 Base film (silicon oxide film)
203 Amorphous silicon film
204 Active layer
205 Gate insulating film (silicon oxide film)
206 Gate electrode
207 Anodized film
208 Source area
209 Offset gate area
210 Channel formation region
211 Drain region
212 Interlayer insulation film
213 source electrode
214 Drain electrode
401 glass substrate
402 pixel region
403, 404 Peripheral drive circuit
405, 406 Connection wiring
51 Quartz substrate
52 Amorphous silicon film
53 microwave
501 Board loading / unloading chamber
502 Processing chamber for microwave irradiation
503 Heating chamber
504 Exhaust pump
505 Substrate transfer chamber
506, 507 Gate valve
508 Gate valve
510 cassette
511 substrate
512 Gas introduction system
513 Exhaust pump
514 door
515 Substrate stage
516 Microwave Oscillator
517 Waveguide
518 stage
519 Gas introduction system
520 Exhaust pump
521 Heater
522 Robot arm
523 Gas introduction system
524 Exhaust pump

Claims (23)

Forming an amorphous silicon film over a substrate having an insulating surface;
The amorphous silicon film is held in contact with a metal element that promotes crystallization of silicon ,
The method for manufacturing a semiconductor device, wherein a mask for attenuating partially microwaves in a state arranged on the substrate, is crystallized by being irradiated with microwaves to the amorphous silicon film. Forming an amorphous silicon film over a substrate having an insulating surface;
Introducing a metal element which promotes crystallization of silicon in the amorphous silicon film,
The method for manufacturing a semiconductor device, wherein a mask for attenuating partially microwaves in a state arranged on the substrate, is crystallized by being irradiated with microwaves to the amorphous silicon film. In claim 1 or claim 2,
A method for manufacturing a semiconductor device, wherein a mask in which an amorphous silicon film is formed over quartz glass is used as the mask for partially attenuating microwaves. In claim 3,
A method for manufacturing a semiconductor device, wherein the attenuation of the microwave is adjusted by controlling the thickness of an amorphous silicon film on the quartz glass. In any one of Claims 1 thru | or 4,
A method for manufacturing a semiconductor device, wherein the microwave irradiation is performed in a vacuum atmosphere. In any one of Claims 1 thru | or 5 ,
A method for manufacturing a semiconductor device , wherein a frequency of 1 GHz to 10 GHz is used as the microwave. In any one of Claims 1 thru | or 6 ,
A method for manufacturing a semiconductor device , wherein a glass substrate is used as the substrate. In any one of claims 1 to 7,
The method for manufacturing a semiconductor device, characterized in that makes detaching the hydrogen of the amorphous silicon film prior to irradiation of the microwaves. In any one of claims 1 to 8,
The method for manufacturing a semiconductor device characterized by heating after the irradiation of the microwave, the prior Ki珪 Motomaku. In any one of claims 1 to 8,
Manufacturing method of the after microwave irradiation, a semiconductor device, which comprises irradiating a laser beam before Ki珪 Motomaku. In any one of claims 1 to 10,
One or more elements selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au are used as the metal element for promoting crystallization of silicon. Device fabrication method. A method for manufacturing an active matrix display device having a pixel region on a substrate having an insulating surface and a peripheral driver circuit for driving a thin film transistor disposed in the pixel region. The
Forming an amorphous silicon film on the substrate;
The amorphous silicon film is held in contact with a metal element that promotes crystallization of silicon,
In a state where a mask for attenuating microwaves is disposed on the substrate in a region where the pixel region is formed, the amorphous silicon film is irradiated with microwaves to be crystallized,
A thin film transistor disposed in the pixel region is formed using the region where the pixel region is formed in the silicon film, and is disposed in the peripheral driving circuit using a region other than the region where the pixel region is formed. A method for manufacturing an active matrix display device, comprising forming a thin film transistor. A method for manufacturing an active matrix display device having a pixel region on a substrate having an insulating surface and a peripheral driver circuit for driving a thin film transistor disposed in the pixel region,
Forming an amorphous silicon film on the substrate;
Introducing a metal element that promotes crystallization of silicon into the amorphous silicon film;
In a state where a mask for attenuating microwaves is disposed on the substrate in a region where the pixel region is formed, the amorphous silicon film is irradiated with microwaves to be crystallized,
A thin film transistor disposed in the pixel region is formed using the region where the pixel region is formed in the silicon film, and is disposed in the peripheral driving circuit using a region other than the region where the pixel region is formed. A method for manufacturing an active matrix display device, comprising forming a thin film transistor. In claim 12 or claim 13,
In the region where the pixel region is formed, the pixel region is formed in the silicon film by irradiating the amorphous silicon film with microwaves in a state where a mask for attenuating microwaves is disposed on the substrate. A method for manufacturing an active matrix display device, wherein crystallinity other than a region to be formed is higher than crystallinity of a region in which the pixel region is formed. In any one of Claims 12-14,
A method for manufacturing an active matrix display device, wherein a mask in which an amorphous silicon film is formed over quartz glass is used as a mask for attenuating microwaves in a region where the pixel region is formed. In claim 15,
A method for manufacturing an active matrix display device, wherein the attenuation of the microwave is adjusted by controlling the thickness of an amorphous silicon film on the quartz glass. In any one of Claims 12-16,
A method for manufacturing an active matrix display device, wherein the microwave irradiation is performed in a vacuum atmosphere. In any one of Claims 12 thru | or 17,
A method for manufacturing an active matrix display device, wherein a frequency of 1 GHz to 10 GHz is used as the microwave. In any one of Claims 12-18,
A method for manufacturing an active matrix display device, wherein a glass substrate is used as the substrate. In any one of Claims 12 to 19,
A method for manufacturing an active matrix display device, wherein hydrogen in the amorphous silicon film is released before the microwave irradiation. In any one of Claims 12 to 20,
A method for manufacturing an active matrix display device, wherein the silicon film is heated after the microwave irradiation. In any one of Claims 12 to 21,
A method for manufacturing an active matrix display device, wherein the silicon film is irradiated with laser light after the microwave irradiation. In any one of Claims 12 to 22,
One or more elements selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au are used as the metal element for promoting the crystallization of silicon. A method for manufacturing a matrix display device.

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