JP4118591B2 - Method for manufacturing display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention disclosed in this specification relates to a technique for forming a crystalline silicon film having a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal on a substrate having an insulating surface such as glass. The present invention also relates to a technique for forming a thin film semiconductor device typified by a thin film transistor by using this crystalline silicon film.
[0002]
[Prior art]
In recent years, a technique for forming a thin film transistor using a thin film silicon semiconductor film (having a thickness of about several hundred to several thousand Å) formed on a glass substrate or a substrate having an insulating surface has attracted attention. Thin film transistors are most expected to be applied to active matrix liquid crystal display devices.
An active matrix liquid crystal display device has a structure in which liquid crystal is held between a pair of glass substrates. In addition, a thin film transistor is arranged on each of the pixel electrodes arranged in a matrix of several hundreds × several hundreds. In such a configuration, a technique for forming a thin film transistor on a glass substrate is required.
[0003]
In order to form a thin film transistor on a glass substrate, it is necessary to form a thin film semiconductor for forming the thin film transistor on the glass substrate. As a thin film semiconductor formed on a glass substrate, an amorphous silicon film (amorphous silicon film) formed by a plasma CVD method or a low pressure thermal CVD method is generally used.
[0004]
At present, thin film transistors using amorphous silicon films have been put into practical use, but in order to obtain a higher quality display, crystalline silicon semiconductor thin films (called crystalline silicon films) were used. A thin film transistor is required.
[0005]
As a method for forming a crystalline silicon film on a glass substrate , techniques described in Japanese Patent Application Laid-Open Nos. 6-232059 and 6-244103 by the present applicant are known. The technique described in this publication uses a metal element that promotes the crystallization of silicon to convert a crystalline silicon film into a glass by heat treatment at 550 ° C. for about 4 hours, which is a heating condition that the glass substrate can withstand. It is formed on a substrate.
[0006]
However, the crystalline silicon film obtained by the method using the above technique cannot be used for a thin film transistor for constituting various arithmetic circuits, memory circuits, and the like. This is because the crystallinity is insufficient and required characteristics cannot be obtained.
[0007]
A peripheral circuit of an active matrix type liquid crystal display device or a passive type liquid crystal display device includes a driving circuit for driving a thin film transistor arranged in a pixel region, a circuit for handling and controlling a video signal, and a memory for storing various information. A circuit or the like is required.
[0008]
Among these circuits, a circuit for handling and controlling video signals and a memory circuit for storing various kinds of information are required to have performance comparable to that of an integrated circuit using a known single crystal wafer. Therefore, when these circuits are to be integrated using a thin film semiconductor formed on a glass substrate, it is necessary to form a crystalline silicon film having crystallinity comparable to a single crystal on the glass substrate.
[0009]
As a method for increasing the crystallinity of the crystalline silicon film, it is conceivable that the obtained crystalline silicon film is subjected to heat treatment again or irradiated with laser light. However, it has been found that it is difficult to dramatically improve the crystallinity even when the heat treatment and the laser light irradiation are repeated.
[0010]
Also, a technique for obtaining a single crystal silicon thin film by utilizing SOI technology has been studied. However, since a single crystal silicon substrate cannot be used for a liquid crystal display device, the technology should be used directly for a liquid crystal display device. I can't. In particular, when a single crystal wafer is used, since the substrate area is limited, it is difficult to use the SOI technology for a liquid crystal display device having a large area for which demand is expected to increase in the future.
[0011]
[Problems to be solved by the invention]
In the invention disclosed in this specification, a region that can be regarded as a single crystal or a single crystal is formed over a substrate having an insulating surface, particularly a glass substrate, and a thin film semiconductor device typified by a thin film transistor is formed using the region. Let it be an issue.
[0012]
[Means for Solving the Problems]
One of the inventions disclosed in this specification is:
Forming a first semiconductor film over a substrate having an insulating surface; crystallizing the first semiconductor film by applying energy; and
Forming a region to be a seed crystal by patterning the first semiconductor film;
Selectively leaving a predetermined crystal plane in the seed crystal by etching;
Forming a second semiconductor film covering the seed crystal;
Performing crystal growth from the seed crystal in the second semiconductor film by applying energy;
It is characterized by having.
[0013]
In the above configuration, a silicon film is typically used as the first and second semiconductor films. In general, an amorphous silicon film formed by a CVD method is used as the silicon film.
[0014]
The reason why the predetermined crystal plane is selectively left is to perform crystal growth so that the crystal becomes closer to a single crystal. The predetermined crystal plane may be left by using an etching means having selectivity with respect to the predetermined crystal plane. For example, by using an etchant in which H ₂ O is mixed at a weight mixing ratio of 63.3 wt%, KOH is 23.4 wt%, and isopropanol is 13.3 wt%, the (100) plane can be selectively left. As a result, the seed crystal covered with the (100) plane can be selectively left.
[0015]
Further, by performing etching in a gas phase using hydrazine (N ₂ H ₄ ), the (111) plane can be selectively left. Specifically, the (111) plane can be left by dry etching using ClF ₃ and N ₂ H ₄ as etching gases.
[0016]
In addition, the method of applying energy in the above configuration is selected from heating, laser light irradiation, and strong light irradiation, and one or more methods can be used simultaneously or stepwise. For example, laser light irradiation while heating, laser light irradiation after heating, heating and laser light irradiation can be performed alternately, or heating can be performed after laser light irradiation. Further, strong light may be used instead of laser light.
[0017]
When a silicon film is used as a semiconductor film and energy is applied to crystallize the silicon film, it is useful to use a metal element that promotes crystallization of silicon. For example, when an amorphous silicon film formed by a plasma CVD method or a low pressure thermal CVD method is to be crystallized by heating, a heat treatment for 10 hours or more is required at a temperature of 600 ° C. or higher. When a metal element that promotes crystallization is used, a heat treatment at 550 ° C. for 4 hours can obtain a result equivalent to or higher than that.
[0018]
As a metal element that promotes crystallization of silicon, nickel is the most effective and useful. One or more elements selected from Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au can also be used. In particular, Fe, Pd, Pt, Cu, and Au can obtain an effect next to Ni.
[0019]
By performing crystal growth from the seed crystal, a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal can be formed in a predetermined region. A region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal is defined as a region that satisfies the following conditions.
-Grain boundaries are not substantially present.
・ Hydrogen or halogen element for neutralizing point defects is contained at a concentration of 0.001 to 1 atomic%.
Contains carbon and nitrogen atoms at a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁸ atoms cm ⁻³ ;
Oxygen atoms are contained at a concentration of 1 × 10 ^{17 to} 5 × 10 ¹⁹ atoms cm ⁻³ .
[0020]
Other aspects of the invention are:
Forming a first silicon film on a substrate having an insulating surface;
A step of contacting and holding a metal element that promotes crystallization of silicon on the first silicon film;
Crystallization of the first silicon film by applying energy;
Forming a region to be a seed crystal by patterning the first silicon film;
Selectively leaving a predetermined crystal orientation in the seed crystal by etching;
Forming a second silicon film covering the seed crystal;
A step of contacting and holding a metal element that promotes crystallization of silicon on the first silicon film;
Performing crystal growth from the seed crystal in the second silicon film by applying energy;
It is characterized by having.
[0021]
Other aspects of the invention are:
Forming a first silicon film on a substrate having an insulating surface;
Crystallization of the first silicon film by applying energy;
Forming a region to be a seed crystal by patterning the first silicon film;
Selectively leaving a predetermined crystal orientation in the seed crystal by etching;
Forming a second silicon film covering the seed crystal;
Performing crystal growth from the seed crystal in the first silicon film by applying energy;
Forming an active layer of a semiconductor device by performing patterning including removing at least a region where the seed crystal is formed;
It is characterized by having.
[0022]
The above structure is characterized in that the region of the obtained active layer is a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal. This region is substantially free of grain boundaries, contains hydrogen or a halogen element for neutralizing point defects at a concentration of 0.001 to 1 atomic%, and contains carbon and nitrogen atoms. It is defined as a region containing a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁸ atoms cm ⁻³ and containing oxygen atoms at a concentration of 1 × 10 ^{17 to} 5 × 10 ¹⁹ atoms cm ⁻³ .
[0023]
Other aspects of the invention are:
Forming a first silicon film on a substrate having an insulating surface;
Crystallization of the first silicon film by applying energy;
Forming a region to be a seed crystal by patterning the first silicon film;
Selectively leaving a predetermined crystal orientation in the seed crystal by etching;
Forming a second silicon film covering the seed crystal;
Forming a second silicon film in a rectangular shape by patterning;
Performing crystal growth from the seed crystal in the second silicon film by applying energy;
Forming an active layer of a semiconductor device by performing patterning on the second silicon film including removing at least a region where the seed crystal is formed;
Have
The seed crystal is located at a corner portion of the second silicon film formed in the rectangular shape.
[0024]
A specific example using the above configuration is shown in FIG. In FIG. 3, a seed crystal 303 is positioned at a corner 304 of an amorphous silicon film 302 formed in a rectangular shape, and a laser beam that has been processed into a linear beam from that portion is irradiated while scanning. A configuration for crystallizing the amorphous silicon film 302 is described.
[0025]
FIG. 3 shows an example of patterning the silicon film 302 (amorphous silicon film) in a quadrangular shape, but this may be square or rectangular.
[0026]
Other aspects of the invention are:
Forming a first silicon film on a substrate having an insulating surface;
Crystallization of the first silicon film by applying energy;
Forming a region to be a seed crystal by patterning the first silicon film;
Selectively leaving a predetermined crystal orientation in the seed crystal by etching;
Forming a second silicon film covering the seed crystal;
Forming a second silicon film into a polygonal shape by patterning;
Performing crystal growth from the seed crystal in the second silicon film by applying energy;
Forming an active layer of a semiconductor device by performing patterning on the second silicon film including removing at least a region where the seed crystal is formed;
Have
The seed crystal is positioned at a corner portion of the second silicon film formed in the polygonal shape.
[0027]
A specific example of the above configuration is shown in FIG. In FIG. 4, a seed crystal is positioned at a corner portion 403 of an amorphous silicon film 401 patterned into a home base type pentagon, and a laser beam that has been linearly processed from this portion 403 is scanned. A structure is shown in which the amorphous silicon film 401 is crystallized by irradiation.
[0028]
FIG. 4 shows an example in which the silicon film is patterned into a pentagon, but this may be a polygon with more corners. However, as the number of corners increases, the angle of the corners inevitably increases, and the effect of promoting crystallization from the corners decreases.
[0029]
Other aspects of the invention are:
Forming a first silicon film on a substrate having an insulating surface;
Crystallization of the first silicon film by applying energy;
Forming a region to be a seed crystal by patterning the first silicon film;
Selectively leaving a predetermined crystal plane in the seed crystal by etching;
Forming a second silicon film covering the seed crystal;
Performing crystal growth from the seed crystal in the second silicon film by applying energy;
Patterning the second silicon film and removing at least a portion where the seed crystal exists;
Have
In the second silicon film after the patterning, 0.001 to 1 atm% of hydrogen is contained, and a metal element that promotes crystallization of silicon is 1 × 10 ¹⁶ atoms to 1 × 10 ¹⁹ atoms cm ^−. It is contained at a concentration of ³ .
[0030]
In the above configuration, as the first and second silicon films, silicon films formed by plasma CVD or reduced pressure thermal CVD are typically used.
[0031]
The reason why the predetermined crystal plane is selectively left is to perform crystal growth so that the crystal becomes closer to a single crystal. The predetermined crystal plane may be left by using an etching means having selectivity with respect to the predetermined crystal plane. For example, by using an etchant in which H ₂ O is mixed at a weight mixing ratio of 63.3 wt%, KOH is 23.4 wt%, and isopropanol is 13.3 wt%, the (100) plane can be selectively left. As a result, the seed crystal covered with the (100) plane can be selectively left. This is because the etching rate of the etchant with respect to the (100) plane is lower than other crystal planes.
[0032]
Further, by performing etching in a gas phase using hydrazine (N ₂ H ₄ ), the (111) plane can be selectively left. Specifically, the (111) plane can be left by dry etching using ClF ₃ and N ₂ H ₄ as etching gases. This is also because the etching rate of hydrazine with respect to the (111) plane is lower than other crystal planes.
[0033]
In addition, as a method of applying energy in the above configuration , one or more kinds of methods selected from heating, laser light irradiation, and strong light irradiation can be used simultaneously or stepwise. For example, laser light irradiation while heating, laser light irradiation after heating, heating and laser light irradiation can be performed alternately, or heating can be performed after laser light irradiation. Further, strong light may be used instead of laser light.
[0034]
When a silicon film is used as a semiconductor film and energy is applied to crystallize the silicon film, it is useful to use a metal element that promotes crystallization of silicon. For example, when an amorphous silicon film formed by a plasma CVD method or a low pressure thermal CVD method is to be crystallized by heating, a heat treatment for 10 hours or more is required at a temperature of 600 ° C. or higher. When a metal element that promotes crystallization is used, a heat treatment at 550 ° C. for 4 hours can obtain a result equivalent to or higher than that.
[0035]
As a metal element that promotes crystallization of silicon, nickel is the most effective and useful. One or more elements selected from Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au can also be used. In particular, Fe, Pd, Pt, Cu, and Au can obtain an effect next to Ni.
[0036]
By performing crystal growth from the seed crystal, a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal can be formed in a predetermined region. A region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal is defined as a region that satisfies the following conditions.
-Grain boundaries are not substantially present.
・ Hydrogen or halogen element for neutralizing point defects is contained at a concentration of 0.001 to 1 atomic%.
Contains carbon and nitrogen atoms at a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁸ atoms cm ⁻³ ;
Oxygen atoms are contained at a concentration of 1 × 10 ^{17 to} 5 × 10 ¹⁹ atoms cm ⁻³ .
[0037]
Further, by removing the region where the seed crystal is present, the concentration of the metal element in the region which can be regarded as the single crystal or the region which can be regarded as the single crystal is 1 × 10 ¹⁶ to 1 × 10 ¹⁹ atoms cm ^−3. , Preferably 1 × 10 ^{16 to} 5 × 10 ¹⁸ atoms cm ⁻³ .
[0038]
[Action]
A seed crystal that can be selectively regarded as a single crystal or substantially regarded as a single crystal is formed, and then an amorphous silicon film is formed so as to cover the seed crystal, and energy is applied by heating or laser light irradiation. Thus, crystal growth can proceed from the seed crystal. A region that can be regarded as a single crystal or a region that can be substantially regarded as a single crystal can be formed around the seed crystal.
[0039]
The region that can be regarded as a single crystal or the region that can be regarded as a substantially single crystal can be formed in a desired region by selecting a region where a seed crystal is formed. Therefore, a thin film semiconductor device formed using this region can be formed in a desired region.
[0040]
That is, a device comparable to a device using single crystal silicon can be formed in a desired region. In addition, a glass substrate that is vulnerable to heating can be used by utilizing the action of a metal element that promotes crystallization of silicon, or irradiation with laser light or strong light.
[0041]
A plurality of semiconductor regions obtained by patterning a region that can be regarded as one single crystal or a region that can be regarded as substantially a single crystal share the same crystal axis and the rotation angle around it. Here, the crystal axis in FIG. 9 refers to a crystal axis 901 in a direction perpendicular to a plane 903 of a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal.
[0042]
The starting film in the direction of the crystal axis may vary depending on the film formation method, the crystallization method, and the method. Specifically, values such as the <111> axial direction and the <100> axial direction are taken.
[0043]
The rotation angle around the crystal axis refers to an angle indicated by 902 shown in FIG. This angle is a relative angle measured with reference to an arbitrary direction.
[0044]
In a region that can be regarded as the same single crystal or a region that can be regarded as substantially a single crystal, the crystal axis and the rotation angle around the region are the same or substantially the same in the region.
[0045]
Here, the same or substantially the same crystal axis is defined as that the angle of blur falls within a range of ± 10 °. Further, the same or substantially the same rotation angle is defined as that the angle of shake falls within a range of ± 10 °.
[0046]
Therefore, when a plurality of semiconductor regions are formed by patterning a region that can be regarded as the same single crystal or a region that can be regarded as a substantially single crystal, and a plurality of thin film transistors are formed using the regions, The crystal axes are the same. The angle around the crystal axis is also the same.
[0047]
By utilizing this, a plurality of thin film transistors using a region that can be regarded as a single crystal sharing the same crystal axis and the surrounding angle or a region that can be regarded as a substantially single crystal are formed as one group. Can do. For example, a CMOS circuit or an inverter circuit formed by combining P-channel and N-channel thin film transistors can be regarded as a single crystal or a single crystal that shares the same crystal axis and the surrounding angle. Can be configured with regions.
[0048]
【Example】
[Example 1]
In this embodiment, a crystalline silicon film is first formed on a glass substrate, and a pattern to be a seed crystal is formed by patterning the crystalline silicon film. Then, an amorphous silicon film is formed and subjected to a heat treatment to cause crystal growth using this seed crystallinity as a seed, thereby forming a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal. .
[0049]
Hereinafter, a manufacturing process of the crystalline silicon film shown in this embodiment will be described with reference to FIG. First, a silicon oxide film 102 serving as a base film is formed on the glass substrate 101 to a thickness of 3000 mm by plasma CVD or sputtering. This silicon oxide film functions as a barrier film for preventing mobile ions from the glass substrate from entering the semiconductor film and preventing other impurities from diffusing to the semiconductor.
[0050]
Next, an amorphous silicon film is formed to a thickness of 1000 mm by plasma CVD or low pressure thermal CVD. Further, a nickel film 104 is formed on the surface of the amorphous silicon film by vapor deposition or sputtering. The nickel film has a thickness of 200 mm.
[0051]
After the nickel film is formed, heat treatment is performed at a temperature of 300 ° C. to 500 ° C., here 450 ° C., for 1 hour to form a nickel silicide layer at the interface between the nickel film 104 and the amorphous silicon film 103. . Since this heat treatment is for forming a nickel silicide layer, the heat treatment is performed at a temperature of 500 ° C. or less at which the amorphous silicon film 103 is not crystallized, taking about 1 to 2 hours. (Fig. 1 (A))
[0052]
Alternatively, the nickel silicide layer may be formed by performing laser light irradiation instead of the heat treatment. Further, the nickel silicide layer may be formed by using heating and laser light irradiation in combination.
[0053]
When the nickel silicide layer is formed at the interface between the nickel film 104 and the amorphous silicon film 103, heat treatment for crystallizing the amorphous silicon film 103 is performed. This heat treatment is performed at 550 ° C. for 4 hours. The upper limit of the heat treatment conditions is determined by the heat-resistant temperature of the glass substrate. Although crystallization is possible even at a temperature of about 500 ° C., the processing time becomes 10 hours or more, so the productivity is deteriorated.
[0054]
Further, the amorphous silicon film 103 may be crystallized by irradiation with laser light or strong light instead of heat treatment. Further, it is more effective to use laser light or intense light irradiation and heating in combination. It is also effective to perform heating after laser light irradiation. It is also effective to repeat the laser light irradiation and heating alternately.
[0055]
The crystallization by the heat treatment is performed using the nickel silicide component of the nickel silicide layer as a crystal nucleus. When such a method is adopted, the nickel concentration in the obtained crystalline silicon film is very high (about 10 ²⁰ atoms cm ⁻³ or more) and cannot be used as it is for a semiconductor device. . However, its crystallinity can be very high.
[0056]
When crystallization by heat treatment is completed, etching is performed using FPM to selectively remove the nickel film and nickel silicide. FPM is a solution of hydrofluoric acid with excess water, and has an action of selectively removing impurities contained in silicon. In this case, the nickel film and the nickel silicide layer can be selectively removed. Further, the nickel component of the obtained crystalline silicon film can be removed.
[0057]
A crystalline silicon film 105 is thus obtained. This crystalline silicon film has excellent crystallinity, but cannot be used for a semiconductor device as it is because of its high internal nickel concentration. (Fig. 1 (B))
[0058]
Next, patterning is performed to form island-like regions 106 and 107 that become seeds for crystal growth (hereinafter referred to as seed crystals). This island-shaped region has a size of 0.1 μm to several tens of μm square. The size of this patterning needs to be 0.1 to 5 μm square, preferably 0.1 to 2 μm square. This is to obtain single crystallinity of the seed crystal. In this state, etching is further performed by FPM (an etchant obtained by adding perhydrous to hydrofluoric acid) to remove the nickel component exposed on the surface of the seed crystal.
[0059]
Then, the island-shaped regions 106 and 107 are irradiated with laser light, thereby increasing the crystallinity of the island-shaped regions. At this time, since the island-shaped region is a minute region, it can be transformed into a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal. Thus, seed crystals 106 and 107 can be obtained. (Figure 1 (C))
[0060]
During the laser irradiation, it is important to heat the irradiated region at a temperature in the range of 450 ° C. to the strain point of the glass substrate. The higher the heating temperature, the greater the effect. However, in consideration of the heat resistance of the glass substrate, it is necessary to set it below the strain point of the glass substrate to be used. Note that when a substrate having heat resistance such as a quartz substrate or a semiconductor substrate is used, the substrate may be heated at a high temperature of about 800 ° C. to 1000 ° C. Further, as a heating method, a method using a heater or a method using irradiation with infrared light or other strong light may be employed.
[0061]
Next, chemical etching is performed to leave crystal faces having specific orientations in the seed crystals 106 and 107. For example, by using an etchant in which H ₂ O is mixed at a weight mixing ratio of 63.3 wt%, KOH is 23.4 wt%, and isopropanol is 13.3 wt%, the (100) plane can be selectively left. As a result, the seed crystal covered with the (100) plane can be selectively left.
[0062]
Further, by performing etching in a gas phase using hydrazine (N ₂ H ₄ ), the (111) plane can be selectively left. Specifically, the (111) plane can be left by dry etching using ClF ₃ and N ₂ H ₄ as etching gases. That is, hydrazine has the highest etching rate on the (100) plane, and the etching rate on the (111) plane is extremely low. Also, the etching rate for other crystal planes is larger than that for the (111) plane. Therefore, the (111) plane can be selectively left by etching using hydrazine.
[0063]
Region thus obtained seed crystals, Yes to removed as much as possible the nickel components (but is Tsu bets on the semiconductor device, the nickel at a concentration level that a negative effect is present), also can be regarded as a single crystal Alternatively, since it is composed of a region that can be regarded as a single crystal, it can function as a nucleus for crystal growth in subsequent crystal growth.
[0064]
Next, an amorphous silicon film 108 is formed to a thickness of 300 mm on the entire surface so as to cover the seed crystal. The amorphous silicon film is formed by a plasma CVD method or a low pressure thermal CVD method. In particular, considering the point of step coverage, it is preferable to use a low pressure thermal CVD method. Then, the amorphous silicon film 108 is crystallized by performing heat treatment. Here, the amorphous silicon film 108 is crystallized by performing a heat treatment at 600 ° C. for 8 hours.
[0065]
In this step, crystal growth proceeds using seed crystals 106 and 107 as nuclei. Thus, regions 108 and 109 that can be regarded as single crystals or regions that can be regarded as substantially single crystals are formed. In this crystal growth, the exposed crystal face of the seed crystals 106 and 107 grows. For example, when the (100) plane is selectively left in the seed crystal, the upper surfaces of the regions 110 and 109 have the (100) plane.
[0066]
Crystal growth proceeds toward the periphery of the seed crystals 106 and 107. A crystal grain boundary 111 is formed where the crystal growth from the seed crystal 106 and the crystal growth from the seed crystal 107 collide with each other.
[0067]
FIG. 2 shows a state where the state of crystal growth is viewed from the top. FIG. 2 shows how crystal growth proceeds from the two seed crystals 106 and 107. A cross section taken along line AA ′ in FIG. 2 corresponds to the state shown in FIG.
[0068]
A region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal shown by 109 and 110 in FIGS. 1 and 2 can have a radius of several tens μm to several hundreds μm or more.
[0069]
What is important here is that by controlling the position where the seed crystal is formed, the place where the region that can be regarded as a single crystal or the region that can be regarded as substantially a single crystal can be arbitrarily controlled.
[0070]
Finally, the seed crystals 106 and 107 are removed by etching. Thus, the step of forming a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal on the glass substrate is completed. Thereafter, various thin film semiconductor devices may be formed according to a known process.
[0071]
When the structure shown in this embodiment is employed, a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal can be formed in any place on the glass substrate.
[0072]
Further, the concentration of nickel element in a region that can be regarded as a single crystal after removal of a region that can be regarded as a seed crystal (after patterning) or a region that can be regarded as a substantially single crystal is 1 × 10 ¹⁶ atoms to 1 × 10 ^19. Atom cm ⁻³ , more preferably 1 × 10 ¹⁶ atoms to 5 × 10 ¹⁸ atoms cm ⁻³ . By using this region, a thin film semiconductor device with little influence of nickel can be realized.
[0073]
[Example 2]
In this embodiment, as shown by an arrow 305 by irradiating a linear laser beam while scanning from a corner portion 304 of an amorphous silicon film 302 formed in a rectangular shape as shown in FIG. Crystal growth is performed in the direction.
[0074]
In this case, seed crystals 303 are formed in corner portions 304 of the amorphous silicon film 302 processed into a rectangular shape. In order to realize such a state, first, the seed crystal 303 is formed on the glass substrate 300 by the method described in the first embodiment, and an amorphous silicon film is further formed. Then, by patterning the amorphous silicon film so as to be rectangular, a state as shown in FIG. 3 is obtained.
[0075]
When laser light irradiation is performed in the state as shown in FIG. 3, the crystal growth proceeds in a direction in which the area gradually increases, so that the rectangular amorphous silicon film 302 is changed to a single crystal. The region can be transformed into a region that can be regarded as a single crystal.
[0076]
In FIG. 3, only one amorphous silicon film 302 is shown for simplicity of description, but the number may be provided as required. However, it is important to align that direction.
[0077]
When a region that can be regarded as a single crystal or a region that can be regarded as a single crystal is obtained, patterning is performed to form an active layer of the thin film transistor. At this time, it is important to remove the portion of the seed crystal 303. For example, the size of the amorphous silicon film indicated by 302 patterned in a rectangular shape is set to several tens to several hundreds of percent from the required active layer of the thin film transistor, and is patterned after the completion of crystallization. good is, it may be used as the active layer.
[0078]
Example 3
In this embodiment, a non-linear silicon film 401 processed into a shape as shown in FIG. 4 is irradiated with a linear laser beam 402 from its corner portion 403 while scanning. The crystalline silicon film 401 is transformed into a region that can be regarded as a single crystal or a region that can be regarded as a single crystal substantially. In the state shown in FIG. 4, a seed crystal 404 is formed at a starting portion 403 where crystal growth starts. The seed crystal 404 may be formed by the method shown in the first embodiment.
[0079]
When irradiation is performed while scanning with laser light in the state as shown in FIG. 4, crystallization proceeds in a direction in which the area gradually increases, so that the entire amorphous silicon film 401 can be finally regarded as a single crystal. Alternatively, it can be transformed into a region substantially regarded as a single crystal.
[0080]
When a region that can be regarded as a single crystal or a region that can be regarded as a single crystal is obtained, patterning is performed to form, for example, an active layer of a thin film transistor. At this time, it is important to remove the portion of the seed crystal 404.
[0081]
Example 4
In this embodiment, an example in which a circuit in which a P-channel thin film transistor and an N-channel thin film transistor are configured to be complementary is formed by applying the method described in Embodiment 1.
[0082]
First, the state shown in FIG. 5A is obtained by the method shown in the first embodiment. The state shown in FIG. 5A is the same as the state shown in FIG. After obtaining the state shown in FIG. 5A, patterning is performed to form active layers 501 and 502 of thin film transistors. In this patterning step, the seed crystals 106 and 107 and the region of the crystal grain boundary 111 are removed. This area of the seed crystal, the nickel element has been utilized in the crystallization step is present in high concentrations, also impurities at the grain boundaries is either et segregated.
[0083]
The concentration of nickel element in the regions 501 and 502 that can be regarded as single crystals or substantially regarded as single crystals thus obtained is 5 × 10 ¹⁸ atoms / cm ³ or less, and the presence of nickel atoms is particularly problematic. Don't be.
[0084]
In this embodiment, a region indicated by 501 is an active layer of an N-channel thin film transistor. A region indicated by 502 is an active layer of a P-channel thin film transistor. Next, a silicon oxide film 503 functioning as a gate insulating film is formed to a thickness of 1000 mm. Further, gate electrodes 504 and 505 are formed by forming an N-type microcrystalline silicon film doped with a large amount of phosphorus by low-pressure thermal CVD and patterning. (Fig. 5 (C))
[0085]
Further, in this state, in the state where each thin film transistor region is covered with a resist mask, phosphorus and boron ions are alternately implanted, and a source region 506, a drain region 508, and a channel formation region 507 of an N channel type thin film transistor (TFT) Are formed in a self-aligning manner. In addition, a source region 511, a drain region 509, and a channel formation region 510 of a P-channel thin film transistor are formed in a self-aligned manner. (Fig. 5 (C))
[0086]
Next, a silicon oxide film 512 is formed as an interlayer insulating film to a thickness of 6000 mm by plasma CVD. Further, contact holes are formed, and source electrodes 513 and 516 and drain electrodes 514 and 515 are formed with a two-layer film of a titanium film and an aluminum film. Here, the drain electrodes 514 and 515 are connected to form a CMOS structure. In this manner, a state in which the N-channel thin film transistor and the P-channel thin film transistor are configured to be complementary as shown in FIG. 5D is obtained.
[0087]
When the configuration shown in this embodiment is adopted, the active layer of each thin film transistor can be configured as a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal, and thus is configured using a single crystal silicon wafer. Characteristics equivalent to those of a transistor can be obtained. Then, an integrated circuit including transistors using single crystal silicon can be formed.
[0088]
Example 5
In this embodiment, the process shown in FIG. 1 is modified. In this embodiment, in the step shown in FIG. 1D, the entire surface of the amorphous silicon film 108 is kept in contact with nickel element, and then heat treatment is performed, whereby amorphous silicon is obtained. The film 108 is crystallized.
[0089]
There are several methods for performing solid-phase crystallization using a metal catalyst for promoting crystallization.
As one of them, a film of a metal catalyst (Ni, Fe, Ru, Rh, Pd, Pd, Os, Ir, Pt, Cu, Au, etc.) is formed by sputtering, electron beam evaporation or the like. In the case of “target formation”, even if the average thickness of the metal coating is 5 to 200 mm, for example 10 to 50 mm, the catalyst is easily formed on the surface to be formed in an island shape.
That is, the metal catalyst becomes fine particles, and the average diameter is 50 to 200 mm, which is easily scattered. At that time, the distance between the fine particles is also separated from each other by about 100 to 1000 mm. That is, a discontinuous layer is formed, and a uniform continuous film may be difficult to form.
These metal islands form nuclei of crystallization, from which crystal growth of the amorphous silicon film on the insulating substrate is performed by heat treatment at 450 to 600 ° C.
[0090]
However, in this technique, the temperature can be lowered by 50 to 100 ° C. compared to the case where the crystallization is performed without using such a catalyst. It was found that the region is a metal region having metallic properties. It is presumed that metal nuclei are probably left as they are.
This metal region acts as a recombination center of electrons and holes in the crystallized semiconductor region, and when a reverse bias voltage is applied to a semiconductor device, particularly a semiconductor device having a PI and NI junction, the PI and NI junctions. Due to the metal region, which is almost always present in the region of the semiconductor device having the above, there is an extremely malicious characteristic such as an increase in leakage current.
For example, when a thin film type TFT having a channel length / channel width = 8 μm / 8 μm is configured, the off current should be about 10 ⁻¹² A, and 10 ⁻¹⁰ to 10 ⁻⁶ A and 10 ² to 10 ^6. It will be twice as large.
[0091]
In order to eliminate such drawbacks, in this embodiment, a “chemical formation” method is provided as a method for forming a metal catalyst film.
This uses a metal compound diluted in a solution (water, isopropyl alcohol, etc.) at a concentration of 1-1000 ppm, typically 10-100 ppm. In particular, an organometallic compound is used.
Below, the example of the metal compound which can be utilized for the chemical formation method is shown.
[0092]
(1) When Ni is used as a catalyst element As a nickel compound, nickel bromide, nickel acetate, nickel oxalate, nickel carbonate, nickel chloride, nickel iodide, nickel nitrate, nickel sulfate, nickel formate, nickel oxide, nickel hydroxide , Nickel acetylacetonate, nickel 4-cyclohexylbutyrate and nickel 2-ethylhexanoate can be used.
Further, Ni may be mixed with at least one selected from benzene, toluene xylene, carbon tetrachloride, chloroform, ether, trichloroethylene, and chlorofluorocarbon, which are nonpolar solvents.
[0093]
(2) When Fe (iron) is used as a catalyst element Materials known as iron salts such as ferrous bromide (FeBr ₂ 6H ₂ O), ferric bromide (FeBr ₃ 6H ₂ O), acetic acid Ferric iron (Fe (C ₂ H ₃ O ₂ ) ₃ xH ₂ O), ferrous chloride (FeCl ₂ 4H ₂ O), ferric chloride (FeCl ₃ 6H ₂ O), ferric fluoride (FeF) ₃ 3H ₂ O), ferric nitrate (Fe (NO ₃ ) ₃ 9H ₂ O), ferrous phosphate (Fe ₃ (PO ₄ ) ₂ 8H ₂ O), ferric phosphate (FePO ₄ 2H ₂₎ Those selected from O) can be used.
[0094]
(3) In the case of using Co (cobalt) as a catalyst element, a material known as a cobalt salt as the compound, for example, cobalt bromide (CoBr6H ₂ O), cobalt acetate (Co (C ₂ H ₃ O ₂ ) ₂ 4H ₂ O), cobalt chloride (CoCl ₂ 6H ₂ O), cobalt fluoride (CoF ₂ xH ₂ O), and cobalt nitrate (Co (No ₃ ) ₂ 6H ₂ O) can be used.
[0095]
(4) When Ru (ruthenium) is used as a catalyst element, a material known as a ruthenium salt, for example, ruthenium chloride (RuCl ₃ H ₂ O) can be used as the compound.
[0096]
(5) When Rh (rhodium) is used as a catalytic element, a material known as a rhodium salt, for example, rhodium chloride (RhCl ₃ 3H ₂ O) can be used as the compound.
[0097]
(6) When Pd (palladium) is used as the catalyst element, a material known as a palladium salt, for example, palladium chloride (PdCl ₂ 2H ₂ O) can be used as the compound.
[0098]
(7) When Os (osnium) is used as a catalyst element, a material known as an osnium salt, for example, osmium chloride (OsCl ₃ ) can be used as the compound.
[0099]
(8) When using Ir (iridium) as a catalyst element, a material known as an iridium salt as the compound, for example, a material selected from iridium trichloride (IrCl ₃ 3H ₂ O) and iridium tetrachloride (IrCl ₄ ) Can be used.
[0100]
(9) When Pt (platinum) is used as a catalyst element, a material known as a platinum salt, for example, platinum chloride (PtCl ₄ 5H ₂ O) can be used as the compound.
[0101]
(10) When Cu (copper) is used as a catalyst element, cupric acetate (Cu (CH ₃ COO) ₂ ), cupric chloride (CuCl ₂ 2H ₂ O), cupric nitrate (Cu (NO) ₃ ) Materials selected from ₂ 3H ₂ O) can be used.
[0102]
(11) When gold is used as a catalytic element, the compound was selected from gold trichloride (AuCl ₃ xH ₂ O), gold chloride (AuHCl ₄ 4H ₂ O), and sodium tetrachloroaurate (AuNaCl ₄ 2H ₂ O). Materials can be used.
[0103]
Each of these can be sufficiently dispersed in a single molecule in a solution.
This solution can be spread over the entire surface to be formed by dropping the solution onto the surface to which the catalyst is added and spin-coating it at a rotational speed of 50 to 500 revolutions per minute (RPM).
At this time, in order to promote uniform wettability with the surface on which the silicon semiconductor is formed, if a silicon oxide film having a thickness of 5 to 100 mm is formed on the surface of the silicon semiconductor, the solution is covered by the surface tension of the liquid. It is possible to sufficiently prevent spotted spots on the forming surface.
[0104]
Further, the addition of interfacial active agent in a liquid, can exhibit a good state of uniform wetting even on silicon without a silicon oxide film semiconductor.
[0105]
These methods are preferable because the metal catalyst can be diffused atomically into the semiconductor through the oxide film, and can be diffused and crystallized without actively forming crystal nuclei (granular particles). is there.
[0106]
Alternatively, an organic metal compound may be uniformly coated, and then treated with ozone (ultraviolet in oxygen (UV)) to form a metal oxide film, which may be used as a starting state for crystallization. In this way, the organic matter is oxidized and can be vaporized and removed as carbon dioxide gas, so that more uniform solid phase growth can be achieved.
[0107]
Further, when spin coating is performed only by low-speed rotation, the metal component in the solution existing on the surface is likely to be supplied onto the semiconductor film more than necessary for solid phase growth. For this reason, after this low speed rotation, the substrate is rotated at 1000 to 10,000 rotations / minute, typically 2000 to 5000 rotations / minute. Then, all excess organometallic can be removed by shaking off the substrate surface, and the surface can be sufficiently dried. It is also effective for quantifying the amount of organic metal present on the surface.
[0108]
Such a chemical formation method can form a continuous layer without forming nuclei of metal particles for crystallization on the semiconductor surface.
Physical formation tends to be an unhomogenious-layer, but chemical formation is very easily a homogeneous-layer.
When such a technical idea is used, when performing thermal crystallization at 450 to 650 ° C., extremely uniform crystal growth can be achieved over the entire surface.
[0109]
As a result, even when a reverse bias voltage is applied to a semiconductor having a P-I and N-I junction formed using a semiconductor film crystallized by this chemical formation method, the leakage is 10 ^−12. Most can be fulfilled in the A level.
In the physical formation method, for example, out of 100 P-I junctions, 90 to 100 leak currents may cause a leak of 10 ⁻¹⁰ to 10 ⁻⁵ A, and even a N-I junction has 100 leak currents. Among them, 50 to 70 may have a large leak current of 10 ⁻¹² to 10 ⁻⁶ A.
On the other hand, in the “chemical formation method”, leakage current is 10 ⁻¹³ to 10 ⁻⁸ A in 100 out of 100 PI junctions, and 0 to 2 out of 100 in NI junctions. 10 ⁻¹³ to 10 ⁻⁸ A, the off-state current is reduced, the leak-leakage film is reduced, and the characteristics are remarkably improved.
[0110]
Further, in the case where a TFT is formed by forming a semiconductor film on the insulating surface, even if the TFT is a P-channel TFT (PIP) or an N-channel TFT (NIN) type, the same remarkable excellent effect can be obtained.
Furthermore, this off-current value can reduce the existence probability of a TFT having a large leak by about one to two orders of magnitude compared to the physical formation method.
However, in order to make a thin film integrated circuit using this TFT, it is required that the probability of existence of a TFT having a large leakage current is further reduced to 1/10 ³ to 1/10 ⁹ .
[0111]
Further, after thermal crystallization with the addition of a catalytic metal by the chemical formation method described above, when a laser beam of 248 nm or 308 nm is irradiated on the surface with an intensity of 250 to 400 mJ / cm ² , Particularly in a region with many components, light absorption is larger than that of a crystallized silicon film. That is, the region that remains as an amorphous structure, such as metal, is optically black. On the other hand, the crystalline component is transparent.
For this reason, it is possible to selectively melt the slight remaining amorphous component by laser light irradiation, disperse the metal component and recrystallize it, and disperse the metal present in the region in atomic level units. Can do.
Then, in this finished film, the existence probability of the metal region can be further reduced, and an increase in leakage current caused by the metal region as a recombination center of electrons and holes is eliminated. As a result, N− Reduce the off current at I-junction and P-I junction to 10 ^-13 to 10 ^-12 A, about 1 to 2 digits, and the number of TFTs is 10 ⁴ to 10 ^8. It can also be 1-3.
[0112]
In this way, the reverse leakage current, that is, Ioff can be reduced by two orders of magnitude, and the existence probability of a leaky TFT can be lowered by up to two orders of magnitude. It is presumed that the organic metal is deposited and concentrated there, and the improvement of the characteristics can be confirmed by the improvement of the performance of the experimental apparatus.
In addition, if an experiment in which a laser beam is irradiated to a thermally crystallized material by a physical forming method is attempted, the metal particles in the starting film become too large in the first place. Even if it is crystallized, the off-current at the time of reverse bias application in the PI and NI junctions may not be able to be reduced at all.
From the above, compared to the formation of a discontinuous layer of a physical metal catalyst and the accompanying thermal crystallization method, the formation of a continuous layer of a chemical metal catalyst, the accompanying thermal crystallization method, and the The semiconductor device formed by using it is easy to obtain a more excellent effect.
[0113]
As a chemical method, there is a method in which a gas of a metal compound, particularly an organometallic compound is formed on a surface to be formed by a CVD method, instead of using a liquid.
As in the case of using a fluid, this method has a remarkable effect in reducing the off current and the existence probability of a TFT having a large leakage current.
In addition, the physical formation method tends to be a non-uniform “isotropic crystal growth method” using a metal nucleus, but the chemical formation method is a uniform “isotropic growth” using a uniform metal catalyst. It can be said that it is easy to obtain crystal growth.
In addition, this chemical method is a method in which crystal growth is performed in a direction transverse to the substrate surface, and the semiconductor is grown from the lower side to the upper side and from the upper side to the lower side perpendicular to the substrate surface. Characteristics can be obtained.
[0114]
In order to keep nickel element in contact with the surface of the amorphous silicon film 108, as described above, a solution containing nickel element is applied to the surface of the amorphous silicon film, and the excess solution is removed by a spinner. State. Here, a nickel acetate solution is used as the solution.
[0115]
When the structure shown in this embodiment is adopted, the temperature required for crystallization can be lowered and the time can be shortened. Specifically, in the configuration shown in Example 1, a heat treatment of 8 hours or more in a heating atmosphere at 600 ° C. is necessary to crystallize the amorphous silicon film 108, but nickel element is used. In this case, the amorphous silicon film 108 can be crystallized under heat treatment conditions of 550 ° C. for 4 hours.
[0116]
However, when the structure shown in this embodiment is employed, the concentration of the metal element in a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal is increased. Therefore, if attention is not paid to the concentration of the metal element to be introduced, the influence of the metal element appears on the characteristics of the obtained device.
[0117]
Specifically, the concentration of the metal element that finally remains needs to be 1 × 10 ¹⁹ atoms cm ⁻³ or less. For example, when the nickel acetate solution is used, the concentration can be adjusted by adjusting the nickel concentration in the solution. If the concentration of the metal element remaining in the silicon film upon crystallization is 1 × 10 ¹⁶ atoms cm ⁻³ or less, the crystallization promoting action cannot be obtained. Therefore, it is necessary to adjust the introduction amount of the metal element so that the metal element exists in the silicon film at a concentration of 1 × 10 ¹⁶ atom cm ⁻³ to 1 × 10 ¹⁹ atom cm ⁻³ .
[0118]
Example 6
In this embodiment, a seed crystal having a (100) plane orientation is used to obtain a region in which the top surface can be regarded as a single crystal having a (100) plane, or a region that can be regarded as a substantially single crystal. An example is shown.
[0119]
FIG. 6 shows a state where a region that can be regarded as a single crystal or a region that can be regarded as a single crystal is formed. In FIG. 6, 62 is a seed crystal. Reference numeral 61 denotes a region that can be regarded as a single crystal obtained by crystal growth from the seed crystal 62 or a region that can be regarded as a substantially single crystal. In addition, a cross section taken along line AA ′ in FIG. 6A is FIG. 6B.
[0120]
A region 61 that can be regarded as a single crystal or a region 61 that can be regarded as a substantially single crystal shown in FIG. 6 is obtained as having a substantially hexagonal shape.
[0121]
A manufacturing process for obtaining the state shown in FIG. 6 is described below. First, a silicon oxide film is formed on a glass substrate as a base film (not shown), and an amorphous silicon film (not shown) is further formed. Then, this amorphous silicon film is crystallized by a method similar to the method shown in the first embodiment. That is, nickel silicide, which is a metal element that promotes crystallization of silicon, is first formed on an amorphous silicon film, and further subjected to heat treatment to crystallize the amorphous silicon film and further pattern it. As a result, a group of the seed crystal 62 is formed. The seed crystal 62 is obtained by irradiation with laser light while heating to 450 ° C. to 600 ° C. (the upper limit of this temperature is determined by the strain point of the glass substrate).
[0122]
Next, an amorphous silicon film is formed in a state of covering the seed crystal, and a predetermined heat treatment is performed, whereby a region 61 that can be regarded as a single crystal or a region 61 that can be regarded as a substantially single crystal can be obtained. This state is shown in FIGS. 6 (A) and 6 (B).
[0123]
Next, the seed crystal 62 and unnecessary portions are removed to obtain active layers 64 and 66 that are regions that can be regarded as single crystals or, in practice, regions that can be regarded as single crystals. Here, as shown in Example 1, the seed crystal 62 contains a metal element (here, nickel) that promotes crystallization of silicon at a high concentration. Therefore, by performing the above-described patterning, it is possible to prevent the characteristics of a device manufactured later due to the influence of nickel element from changing or deteriorating. In this way, the state shown in FIG. 6C can be obtained.
[0124]
In this way, as shown by 63, 64, 65, and 66 in FIG. 6A, an active layer including a region that can be regarded as a single crystal or a region that can be regarded as a single crystal can be obtained. Thereafter, a thin film transistor may be manufactured using this active layer.
[0125]
Example 7
This embodiment shows an example in which the invention disclosed in this specification is applied to an active matrix liquid crystal display device having a configuration in which peripheral circuits are also integrated. FIG. 7 shows a schematic configuration of the present embodiment.
[0126]
In FIG. 7A, peripheral circuits 702 and 703 formed over a glass substrate 701 and pixel regions 704 arranged in a matrix driven by the peripheral circuits are shown. In order to form a liquid crystal display device, a pair of glass substrates on which counter electrodes are formed is prepared, bonded to the substrate shown in FIG. 7A, and liquid crystal is sealed between them to obtain a liquid crystal display.
[0127]
In the structure shown in FIG. 7A, a thin film transistor including a peripheral circuit including a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal, and an amorphous silicon film is used for a pixel region. It is related with the arrangement which arranged. An amorphous silicon film is used as a thin film transistor disposed in a pixel region. A transistor using an amorphous silicon film is sufficient as a performance of a transistor for controlling the flow of charges to and from a pixel electrode. This is because practicality can be obtained. In particular, in the case of a TN type liquid crystal that is widely used at present, a thin film transistor composed of a silicon thin film having crystallinity comparable to a single crystal has a transistor operating speed that is too high compared to the response speed of the liquid crystal. , Lack of stability of operation. Therefore, it is highly practical in terms that a peripheral circuit capable of high-speed operation is composed of a thin film transistor comparable to a thin film transistor using single crystal silicon and a thin film transistor disposed in a pixel region is composed of an amorphous silicon film. It becomes.
[0128]
FIG. 7B is an enlarged view of a part of the peripheral circuit 703 shown in FIG. An inverter circuit constituting a part of the peripheral circuit is shown in FIG. In practice, a complicated integrated circuit is configured with such an inverter circuit and other required configurations. Note that the peripheral circuit here means at least one of a circuit for driving a thin film transistor arranged in a pixel region, a shift register circuit, and various control circuits and a circuit for handling a video signal. It means the circuit that contains it.
[0129]
In FIG. 7B, reference numeral 705 denotes a seed crystal. Based on this seed crystal, a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal is formed. . Note that at the stage of forming the thin film transistor, a region that can be regarded as a single crystal or a region 708 that can be regarded as a single crystal is patterned with a necessary pattern, and the seed crystal 705 is removed.
[0130]
In FIG. 7B, an N-channel thin film transistor 717 and a P-channel thin film transistor 718 are formed using a region that can be regarded as a single crystal or a region 708 that can be regarded as a substantially single crystal. Thus, an example in which an inverter circuit is configured is shown.
[0131]
Here, an example is shown in which two thin film transistors, an N-channel thin film transistor and a P-channel thin film transistor, are formed in a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal. However, the number of thin film transistors formed in a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal may be formed as many as necessary and possible.
[0132]
A process for manufacturing the structure shown in FIG. 7 will be described below with reference to FIG. FIG. 8 shows a manufacturing process of an inverter circuit formed in the peripheral region and a thin film transistor connected to the pixel electrode formed in the pixel region. In this embodiment, the thin film transistor constituting the peripheral region is configured using a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal. Further, the thin film transistor disposed in the pixel region is formed using an amorphous silicon film.
[0133]
First, a base silicon oxide film 802 is formed on a glass substrate 801 to a thickness of 3000 mm. This glass substrate 801 constitutes one of a pair of glass substrates constituting a liquid crystal display device. Next, a seed crystal 803 is formed by the method shown in the first embodiment. Further, an amorphous silicon film 804 is formed to a thickness of 500 mm. (Fig. 8 (A))
[0134]
Next, by combining heat treatment and laser light irradiation, a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal is formed around the seed crystal 803. Here, excimer laser light of several centimeters is used to irradiate only the peripheral circuit region with laser light. Further, the heating temperature is set to 600 ° C. during the laser light irradiation. Even if heating is performed at a temperature of 600 ° C. for a short time (laser irradiation is for several seconds), the amorphous silicon film is not crystallized, and thus the amorphous silicon film 804 in the pixel region is not crystallized. The heating temperature is preferably as high as possible without causing damage to the glass substrate. Here, in order to heat the silicon film in a short time, a heating method by irradiation with infrared light is used.
[0135]
In this manner, the region indicated by the oblique line 805 in FIG. 8A can be transformed into a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal. In this state, the region other than the hatched line 805 remains as an amorphous silicon film.
[0136]
Next, patterning is performed to form active layers 806 and 807 of thin film transistors disposed in the peripheral circuit. At the same time, an active layer 808 of a thin film transistor connected to the pixel electrode is formed. In this state, the active layers 806 and 807 are formed of a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal. The active layer 808 is composed of an amorphous silicon film.
[0137]
Next, a silicon oxide film 809 functioning as a gate insulating film is formed to a thickness of 1000 mm. Then, an aluminum film containing 0.2 wt% scandium is formed to a thickness of 6000 mm by sputtering or electron beam evaporation, and patterning is performed to form gate electrodes 810, 811 and 812. Furthermore, an anodic oxidation film is formed around the gate electrode by performing anodic oxidation using the gate electrode as an anode in the electrolytic solution. In this way, the state shown in FIG.
[0138]
First, a region where an N-channel thin film transistor is to be formed is masked with a resist mask 800, and B (boron) ions, which are impurities imparting p-type conductivity, are implanted into silicon. Ion implantation is performed using an ion implantation method or a plasma doping method. Further, a region desired to be a P-channel thin film transistor is covered with a resist mask (not shown), and P-ion is implanted. By irradiating laser light (not shown) after completion of these ion implantation steps, activation of the implanted ions and annealing of damage accompanying the ion implantation are performed.
[0139]
Thus, as shown in FIG. 8C, a source region 813 and a drain region 815 of a P-channel thin film transistor (PTFT), and a channel formation region 814 are formed. In addition, a source region 818, a drain region 816, and a channel formation region 817 of an N-channel thin film transistor (NTFT) are formed. These two thin film transistors are arranged in a peripheral circuit, and have an active layer formed of a region that can be regarded as a single crystal or a region that can be regarded as a single crystal (C-Si).
[0140]
In addition, the thin film transistor is formed at the same time as the source region 819, the drain region 821, and the channel formation region 820 of the thin film transistor arranged in the pixel region. The thin film transistor disposed in the pixel region is composed of an amorphous silicon film (a-Si).
[0141]
The step of forming the source / drain regions and the channel formation region by implanting impurity ions is performed in a self-aligned manner.
[0142]
After the source / drain and channel formation regions of each thin film transistor are formed, a silicon oxide film 822 is formed as an interlayer insulating film to a thickness of 6000 mm by plasma CVD. Further, contact holes are formed, a source electrode 823 of a P-channel thin film transistor disposed in the peripheral circuit region, a drain electrode 824 common to the P-channel thin film transistor and the N-channel thin film transistor, and an N-channel thin film transistor. A source electrode 825 is formed. At the same time, a source electrode 826 and a drain electrode 827 of an N-channel thin film transistor which are arranged in the pixel region are formed. These electrodes have a three-layer structure in which an aluminum film is sandwiched between titanium films.
[0143]
Further, an ITO electrode 828 constituting the pixel electrode is formed. In this manner, a thin film transistor that forms a peripheral circuit formed using a region that can be regarded as a single crystal and a thin film transistor that uses an amorphous silicon film disposed in a pixel region can be formed simultaneously on the same glass substrate. In this way, one substrate constituting the active matrix liquid crystal display device shown in FIG. 7 is completed. The structure thus obtained can be regarded as a pair of thin film transistors formed using the seed crystal 805.
[0144]
After obtaining the state shown in FIG. 8D, a second interlayer insulating film is further formed, and an alignment film is formed thereon. Then, a counter electrode is formed on the opposing glass substrate, and an alignment film is also formed. After that, a pair of glass substrates prepared by performing an orientation process are bonded together. Finally, liquid crystal is sealed between the pair of bonded glass substrates to complete an active matrix liquid crystal display panel.
[0145]
The liquid crystal display device as shown in this embodiment has a configuration in which peripheral circuits are integrated, and can be configured to be very compact and lightweight.
[0146]
In this embodiment, as shown in FIG. 8, an example is shown in which a seed crystal 805 is used to form a pair of N-channel and P-channel thin film transistors, which are complementary. However, it may be a pair of thin film transistors of the same channel type. Alternatively, a pair of thin film transistors of N channel type and P channel type may be formed and operated independently.
[0147]
Example 8
In this embodiment, in the structure as shown in FIG. 7A, the pixel region is a passive structure in which a thin film transistor is not used, and crystalline silicon in which only a peripheral circuit can be regarded as a single crystal as shown in FIG. 7B. In this example, the film is composed of a film region or a crystalline silicon film region which can be regarded as substantially a single crystal.
[0148]
If complicated image information is not displayed, it is known that a well-known STN type liquid crystal display device is sufficiently practical. For example, STN type liquid crystal display devices are used in portable information devices (notebook word processors and personal computers) that only need to be able to display letters, numbers, and simple graphics. However, the present situation is that an external IC is used as a peripheral circuit disposed around the pixel region.
[0149]
When an external IC circuit is used, the thickness of the liquid crystal panel is increased and the weight is increased. Therefore, in the configuration shown in this embodiment, only the peripheral circuit is configured as a circuit as shown in FIG. 7B, so that the liquid crystal layer and the peripheral circuit are integrated on the glass substrate. By doing so, a liquid crystal layer between a pair of glass substrates, electrodes and wiring for applying an electric field to the liquid crystal layer, and a periphery as shown by 702 and 703 in FIG. 7A around the liquid crystal layer A circuit can be integrated. Further, since the peripheral circuits 702 and 703 are integrated in a region having a width of several millimeters, the overall configuration can be made very compact.
[0150]
【The invention's effect】
By selectively forming a region to be a seed crystal, a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal can be formed in an arbitrary region. This region can be formed on a glass substrate. When the invention disclosed in this specification is used, a structure in which peripheral circuits of an active matrix liquid crystal display device are integrated on a glass substrate can be realized. In particular, a thin film transistor constituting at least a part of the peripheral circuit can have characteristics equivalent to those using single crystal silicon, which can contribute to further weight reduction and thinning of the liquid crystal display device. The invention disclosed in this specification can be applied to a photoelectric conversion device, an optical sensor, and a pressure sensor using a thin film diode or a thin film semiconductor, besides being applied to a thin film transistor.
[Brief description of the drawings]
FIG. 1 is a diagram showing a process of manufacturing a region which can be regarded as a single crystal or a region which can be regarded as a substantially single crystal.
FIG. 2 is a diagram showing a state where a region that can be regarded as a single crystal or a region that can be regarded as a single crystal has grown.
FIG. 3 is a diagram showing a process of manufacturing a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal by irradiation with laser light;
FIG. 4 is a diagram showing a process of manufacturing a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal by laser light irradiation.
FIGS. 5A and 5B illustrate a process for manufacturing a thin film transistor using a region that can be regarded as a single crystal or a region that can be regarded as a single crystal. FIGS.
6A and 6B are diagrams illustrating a process of manufacturing a region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal.
FIG. 7 illustrates a structure of an active matrix liquid crystal display device.
FIG. 8 is a diagram showing a process of simultaneously forming a thin film transistor in a peripheral circuit and a thin film transistor in a pixel region of an active matrix liquid crystal display device;
FIG. 9 is a diagram for defining a crystal axis and a rotation angle around the crystal axis.
[Explanation of symbols]
101 glass substrate 102 base film (silicon oxide film)
103 Amorphous silicon film 105 Crystalline silicon film 106, 107 Seed crystal 108 Amorphous silicon film 109, 110 Region that can be regarded as a single crystal or a region that can be regarded as a substantially single crystal 111 Grain boundary 501, 502 Active layer 503 Gate Insulating film 504, 505 Gate electrode 512 Interlayer insulating film 513, 516 Source electrode 514, 515 Drain electrode 62 Seed crystal 61, 63-66 Region that can be regarded as single crystal or region that can be regarded as substantially single crystal 701 Glass substrate 702 Peripheral circuit region 703 Peripheral circuit region 704 Pixel region 705 to 707 Seed crystal 708 to 710 Region that can be regarded as single crystal or region that can be regarded as substantially single crystal 717 P channel thin film transistor 718 N channel thin film transistor 801 Glass substrate 802 Base film (silicon oxide) film)
803 Seed crystal 804 Amorphous silicon film 805 Region that can be regarded as single crystal or substantially single crystal 806, 807, 808 Active layer 809 Gate insulating film (silicon oxide film)
810, 811, 812 Gate electrodes 813, 818, 819 Source regions 814, 817, 820 Channel formation regions 815, 818, 821 Drain region 800 Resist mask 822 Interlayer insulating film 823 Source electrode 824 Drain electrode 825 Source electrode 826 Source electrode 827 Drain Electrode 828 Pixel electrode 901 Crystal axis 902 Rotation angle 903 about crystal axis Region that can be regarded as single crystal or region that can be regarded as substantially single crystal

Claims (3)

A method for manufacturing a display device in which a pixel region and a peripheral circuit are formed over the same substrate,
Forming a first amorphous silicon film on the substrate having an insulating surface;
Crystallization of the first amorphous silicon film by applying energy;
Forming a region to be a seed crystal by patterning the crystallized silicon film;
A step of performing dry etching using ClF ₃ and N ₂ H ₄ on the region to be the seed crystal to form a seed crystal with the (111) plane remaining;
Forming a second amorphous silicon film covering the seed crystal;
And a step of growing a part of the second amorphous silicon film from the seed crystal by applying energy,
A region of the second amorphous silicon film that is crystal-grown is used as an active layer of a thin film transistor disposed in the peripheral circuit, and a region of the second amorphous silicon film that is not crystal-grown is A method for manufacturing a display device, which is used as an active layer of a thin film transistor disposed in a pixel region. Oite to claim 1,
The method for manufacturing a display device, wherein the seed crystal is formed in the peripheral circuit and is not formed in the pixel region. Oite to claim 1 or claim 2,
As a method for applying the energy, one or a plurality of methods selected from heating, laser light irradiation, and strong light irradiation are used.

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