JP2000183357A - Thin film transistor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent single crystal thin film transistor by forming an acute-angled groove whose end has a predetermined or a smaller angle in a substrate, embedding semiconductors made of amorphous silicon, fine crystals or the like, and forming a large crystal semiconductor by annealing a semiconductor within the groove. SOLUTION: A groove 2 having an acute-angled end 21 in a region which generally become an active region on the surface of a substrate, the angle of the end 21 being 30 deg. or less. Then, an amorphous silicon (a-Si) film 31 is deposited on the entire surface of the substrate. The film 31 is removed from a region excluding the groove 2, so that a-Si remains only in the groove 2. Thereafter, a beam-shaped laser is injected in the direction of the groove from the end 21 of the groove. According to this constitution, cooling first starts at the end 21 of the groove, and crystallization initially occurs only at this single place. Thereafter, as the laser beam moves, silicon atoms newly precipitate in accordance with fine crystals produced at the end 21. Therefore, a plurality of single crystal silicon regions can be prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor, and more particularly to a method of manufacturing a large crystal thin film transistor using excimer laser annealing and such a thin film transistor.

[0002]

2. Description of the Related Art First, words used in this specification will be described.

[0003] In this specification, "semiconductor" refers in principle to materials such as silicon (silicon, Si) and germanium, and "transistor" refers to vacuum tubes and switches formed using these semiconductors. And the like.

[0004] The term "laser" refers to a laser used for melting and crystallizing a semiconductor at the time of filing the present invention so that the content of the present invention can be easily understood. Melting by irradiation with any other energy such as a beam, if a crystallization means is developed or put into practical use, this is also included in the concept of laser referred to in the present specification unless it is contrary to the gist of the present invention. Of course.

In recent years, thin film transistors (hereinafter referred to as “TF
T), an active matrix liquid crystal display device (LCD) that is driven independently for each pixel is being actively researched and developed. This TFT is roughly classified into a polycrystalline silicon thin film transistor (hereinafter referred to as “pol”).
y-Si TFT ") and amorphous silicon thin film transistor (hereinafter also referred to as" a-Si TFT ").

Conventionally, a-Si T has been used for LCDs.
Although FT was mainly used, poly-Si TFTs having mobility higher by one digit or more have come to be used frequently for miniaturization (high definition) for improving image quality and high-speed driving of pixels. .

[0007] Further, with the increase in the speed of the TFT, the peripheral drive circuit of the LCD has reached a level where it can be integrally formed in the LCD substrate, and by eliminating the connection of the peripheral drive circuit chip, cost reduction and miniaturization of high reliability are achieved. Improvements are being made.

However, in the conventional method of manufacturing a poly-Si TFT, high-temperature processing at or near 1000 ° C. or more is required for annealing (crystallization of amorphous silicon or melting and recrystallization of polysilicon composed of fine particles). Is necessary, so glass cannot be used for the substrate,
Expensive quartz must be used, and thus large LCD
Is difficult to manufacture at low cost.

Therefore, after depositing (forming a film) a-Si on an inexpensive glass substrate using a low-temperature process of 600 ° C. or lower, a-Si is converted into poly-Si by excimer laser annealing (ELA). Therefore, technology for improving the performance of TFTs is being put to practical use.

According to this method, only a semiconductor layer is melted by irradiating an extremely short pulse excimer laser beam to the semiconductor layer to crystallize the semiconductor layer. It forms a semiconductor layer.

By using the ELA method, a poly-Si TFT having high mobility can be manufactured on an inexpensive glass substrate, and high-speed operation of a thin film circuit can be realized.

FIGS. 1A to 1D schematically show the procedure of the ELA method.

Hereinafter, this step will be described in order with reference to FIG.

(A) On a glass substrate 1, S is used as a protective film.
An iO ₂ film 4 is deposited (forming a film on a flat plate or film).

(B) On the glass substrate on which the protective film has been deposited, a-
An Si film 31 is deposited.

(C) The a-Si film is annealed by irradiating the a-Si film with an excimer laser. That is, the portion of the a-Si film irradiated with the laser beam is melted and crystallized during cooling, so that the poly-S
An i film 32 is formed.

(D) An active region 34 is formed by isolating, for example, patterning the poly-Si film corresponding to the arrangement of the transistors in the pixel portion and the drive control circuit portion on the liquid crystal display panel. . Further, after a gate insulating film 5 is formed by depositing an SiO ₂ film by PE-CVD,
By the E-CVD method, n ⁺ po containing a high concentration of phosphorus
After depositing the ly-Si film, patterning is performed to form the gate electrode 6.

Thereafter, although not shown, phosphorus is implanted into the source / drain regions and n ⁺ (or boron is implanted into p ^+
+ ) An impurity layer is formed to form a poly-Si TFT.

[0019]

As described above, a
By performing laser annealing on the -Si film, a poly-Si film can be formed on an inexpensive glass substrate, and a poly-Si TFT can be formed.

However, with the current technology, it is difficult to uniformly heat the entire surface of the a-Si film in the laser irradiation region, that is, due to the energy density variation in the laser beam. The film quality of the poly-Si film in the plane varies. As a result, the characteristics (particularly, mobility) of the poly-Si TFT vary.

Further, when the a-Si film once melted by the laser irradiation is cooled again to form a poly-Si film, small crystal nuclei are randomly formed in the molten silicon at the initial stage, and the cooling proceeds. Accordingly, the nucleus becomes the center of particle growth, and it is very difficult to control the size of each grain (crystal grain) of the poly-Si film. For this reason, even if the particle size is larger than that before the irradiation, the particle size still becomes smaller and irregular as shown in FIG.

Further, since the poly-Si film contains a much larger number of defects than the single crystal silicon (c-Si) film, it is difficult to improve the mobility.

For this reason, it is manufactured using ELA technology,
In addition, there has been a demand for the development of a single crystal thin film transistor having excellent performance without such defects and a manufacturing method therefor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in view of the above problem.
FT ") and a thin film transistor having a performance close thereto.

[0025]

In order to achieve the above object, in the present invention, a nucleus is controlled by forming a groove in a substrate and annealing the amorphous silicon in the groove. Specifically, it is as follows.

According to the first aspect of the present invention, at least the active region of the transistor is finished at the beginning of the laser irradiation for laser annealing (and is often irradiated first) at 30 °. A groove forming step of forming the following acute-angle groove, an annealing target semiconductor burying step of burying a semiconductor made of amorphous, fine crystal or the like in the groove, and an annealing step of turning the annealing target semiconductor in the groove into a large crystal semiconductor by laser annealing And characterized in that:

The following operation is performed by the above configuration.

In the groove forming step, at least the active region of the substrate has a first end of laser irradiation for laser annealing, and often both ends have an acute angle of 30 ° or less. Then, a groove having a depth of preferably 200 nm or less (especially for a glass substrate), more preferably 50 nm or less, is formed.

In the step of burying a semiconductor to be annealed, a semiconductor made of amorphous, fine crystal, or the like is buried in the groove (including, if there is some unfilled).

Further, the semiconductor outside the trench is removed as required.

In the annealing step, the semiconductor to be annealed in the trench is made into a large crystal semiconductor by laser annealing, and in principle, into a single crystal semiconductor. (Depending on the depth and width of the groove or the material of the substrate, a large crystal semiconductor is formed.) Thereafter, a process for forming a transistor as an element is performed.

In the invention described in claim 2, in the groove forming step, the acute angle of the first end of the laser irradiation for the laser annealing is set to 15 ° or less, more preferably 10 °, in order to exert more effect. It is characterized by a sharp angle forming step described below.

The following operation is performed by the above configuration.

In the acute angle forming step of the groove forming step, the acute angle at the first end of the laser irradiation for laser annealing is set to 15 ° or less, more preferably 10 ° or less in order to exhibit more effects.

According to a third aspect of the present invention, the groove forming step is characterized in that the groove is formed independently of each other at least for each region to be an active region of each thin film transistor.

The following operation is performed by the above configuration.

In the groove independent forming step of the groove forming step, the grooves are formed as independent grooves at least for each region (often including the periphery) which will be the active region of each thin film transistor. (Of course, when they are close to each other, a continuous groove may be partially formed.)
In the described invention, the groove forming step is a temporary groove forming small step in which the first end end of laser irradiation is once formed with a temporary groove that is not necessarily acute due to the size and shape of the focal point by using photolithography technology. After the small step, the Si having a thickness of 55% or more of the temporary groove width is formed by CVD.
It is characterized in that it has an acute angle forming small step of forming the O ₂ film on the temporary groove.

The following operation is performed by the above configuration.

In the temporary groove forming small step of the groove forming step, a temporary groove whose first end portion of laser irradiation is not always acute is once formed by using photolithography technology.

After the temporary groove forming small step, an acute angle forming small step forms a SiO ₂ film having a thickness of 55% or more of the temporary groove width on the temporary groove by PE-CVD. Thus, with the current technology, a groove having an acute angle is formed in the glass substrate without difficulty.

According to the fifth aspect of the present invention, at least a portion of the active region of the thin film transistor which has a shape which is continuously connected to the long side direction determined by the transistor arrangement and which is not the active region. A step of forming a concave / convex existing groove having a width smaller than the short side of the active region and a minimum groove width of 0.2 μm or less; The step of embedding the semiconductor to be annealed by any means or the like, and the laser irradiation for turning the semiconductor to be annealed in the premises having the irregularities into a large crystal semiconductor by laser annealing, and in many cases, the irradiation of the laser for forming the single crystal semiconductor with the irregularities And performing an annealing step from one end of the groove to be performed along the groove.

The following operation is performed by the above configuration.

In the step of forming a groove having unevenness, the shape is a continuous shape having no break or extreme unevenness at least in the long side direction of the active region of the thin film transistor on the substrate, and is substantially linear, and The groove width of the portion other than the active region is narrower than the short side of the active region, and the minimum groove width is 0.2 μm or less, and is formed so as to be continuously connected to the wide portion of the active region without any corners.

In the step of embedding a semiconductor to be annealed, a semiconductor made of amorphous, fine crystal, or the like is embedded in a pre-existing structure by any means such as sputtering.

In the annealing step, laser irradiation for turning the semiconductor to be annealed in the premises having irregularities into a large crystal semiconductor by laser annealing is performed along one end of the grooves having irregularities.

After the single-crystal silicon is formed, the silicon is selectively etched by dry etching using a photoresist pattern, impurities are introduced into the remaining silicon in the groove, and the element is formed by P / N junction. By separating, a plurality of active regions having no surface step are formed.

According to a sixth aspect of the present invention, the step of forming an uneven groove includes at least a small step of forming an acute angle groove for forming the laser irradiation start end side for annealing at an acute angle. .

The following operation is performed by the above configuration.

In the acute angle groove forming small step, the laser irradiation start end side for annealing in the unevenness existing groove forming step is formed at an acute angle. Also, as a rule, rather than as needed, both ends are made acute. Thereby, a giant crystal is formed without difficulty.

According to a seventh aspect of the present invention, a groove forming step of forming a groove having a width of 2 μm or less in at least the long side direction of the active region of the thin film transistor on the substrate; An annealing target semiconductor embedding step of embedding a semiconductor such as silicon made of
An annealing step of sequentially performing laser irradiation along the groove and in accordance with a predetermined scanning procedure for turning the semiconductor to be annealed in the groove into a large crystal semiconductor by laser annealing.

The following operation is performed by the above configuration.

In the groove forming step, at least the width 2 of the active region of the thin film transistor on the long side direction of the substrate is formed.
A groove of not more than μm is formed.

In the step of burying a semiconductor to be annealed, a semiconductor such as silicon made of amorphous or fine crystal is buried in the trench.

In the annealing step, laser irradiation for turning a semiconductor to be annealed in the groove into a large crystalline semiconductor by laser annealing is performed by driving one or both of the substrate and the laser irradiation apparatus, and thereby along the groove. Perform sequentially.

According to an eighth aspect of the present invention, the groove forming step includes an acute angle groove forming small step of forming a laser irradiation start end side for annealing at an acute angle in advance.

The following operation is performed by the above configuration.

In the acute angle groove forming step of the groove forming step, the laser irradiation start end side (including both end sides) for annealing is in principle 30 ° or less, preferably 15 ° or less.
More preferably, it is formed at an acute angle of 10 ° or less. Therefore, single-crystal silicon or the like is formed from the end of the groove.

According to the ninth aspect of the present invention, the step of embedding a semiconductor to be annealed includes a small step of depositing a semiconductor to be annealed for depositing a semiconductor made of amorphous, fine crystal, or the like over the entire surface of the substrate for convenience of the process. Removing a semiconductor deposited on the portion.

The following operation is performed by the above configuration.

In the step of depositing the semiconductor to be annealed in the step of burying the semiconductor to be annealed, a semiconductor made of amorphous, fine crystal, or the like is once deposited on the entire surface of the substrate for convenience of the process.

Similarly, in a small removing step, the semiconductor deposited on an unnecessary portion is removed by mechanical or chemical means.

In the tenth aspect of the present invention, prior to the step of embedding a semiconductor to be annealed, amorphous silicon is used as a semiconductor to be annealed and a particle diameter of the semiconductor to be embedded is 0.1 mm.
The method is characterized in that it has a step of selecting a semiconductor to be annealed for selecting at least one of silicon made of fine crystals of 1 μm or less.

The following operation is performed by the above configuration.

In the step of selecting a semiconductor to be annealed prior to the step of embedding the semiconductor to be annealed, there are applications at the time of filing the present invention, the performance of the transistor, the convenience of deposition, and the like. At least one of silicon made of fine crystals of 1 μm or less is selected.

According to the eleventh aspect of the present invention, there is provided a substrate on which a thin film transistor is formed, wherein at least one end is 3
It is characterized by having a groove having an acute angle of 0 ° or less, preferably 15 ° or less, and a large crystal (in principle, a single crystal) semiconductor in the groove.

The following operation is performed by the above configuration.

The substrate on which the thin film transistor is formed has at least one groove whose one end has an acute angle of 30 ° or less and a large crystal semiconductor in the groove. In addition, if you write just in case,
Of course, the end of the groove may be filled with some means or substance (included in the present invention).

According to the twelfth aspect of the present invention, the substrate on which the thin film transistor is formed has a shape continuously connected to the long side direction of the active region of the thin film transistor, and has a groove width of a portion other than the active region. Is characterized by having a groove narrower than the short side of the active region and further having a minimum width of 0.2 μm or less, and a large crystalline semiconductor of the active region in the groove.

The following operation is performed by the above configuration.

The substrate on which the thin film transistor is formed has a shape continuously connected to the long side direction of the active region of the thin film transistor, and the groove width of a portion other than the active region is narrower than the short side of the active region. (It does not matter whether the depth is the same or not), and further has a groove having a minimum width of 0.2 μm or less (in this case, includes a groove trace in which something is embedded). The active region in the groove has a large crystal semiconductor. When the liquid crystal display device is completed, the semiconductor is of course isolated as individual transistors.

According to a thirteenth aspect of the present invention, there is provided a substrate on which a thin film transistor is formed, wherein the width is 2 μm or less continuously connected to the long side direction of the active region of the thin film transistor, and the depth is about 30 to 200 nm. And a large crystalline semiconductor in an active region in the groove.

The following operation is performed by the above configuration.

The substrate on which the thin film transistor is formed has a groove having a width of 2 μm or less continuously connected to the long side direction of the active region of the thin film transistor. The active region in the trench has a large crystal semiconductor such as a single crystal for each active region in order to exhibit a function as a transistor element.

In the invention according to claim 14, the groove is
At least one end has an acute angle of 30 ° or less.

The following operation is performed by the above configuration.

The groove has an acute angle of at least 30 ° at one end. For this reason, there is also an action such as a difference in thermal conductivity between silicon and silicon dioxide, so that single crystallization is performed more quickly than the groove during annealing.

[0077]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on its embodiments.

(First Embodiment) This embodiment is directed to a method of manufacturing a thin film transistor in which at least one end has an acute-angle groove for each transistor, more precisely, a means of large crystallization by laser irradiation of a semiconductor. And a method for manufacturing a transistor in which such a groove is formed.

FIGS. 3 and 4 are views for explaining the entire method of manufacturing the thin film transistor according to the present embodiment, and show how the thin film transistor is formed as the procedure proceeds. In addition, although both figures should originally be drawings of one leaf, they are two leaves for convenience of the sheet size.

The procedure of the manufacturing method according to the present embodiment will be described below with reference to FIGS.

(A) A very thin SiO ₂ protective film (not shown) is formed on the surface of the substrate 1 made of an insulator such as glass.
Grooves 2 are formed. This groove is formed on both sides of the groove.
Are formed outside the active region and further narrowed, and the width A of the narrowed portion is desirably the minimum width possible by using the photolithography technique or a narrow width close thereto. In this embodiment, the groove width A is set to 1 by using g-line or i-line lithography used for general pattern formation.
μm.

In the same manner, the groove width B of the portion to be the active region was set to 5.2 μm. When a pattern is formed using ordinary photolithography technology, the corner of the pattern is necessarily rounded due to the focus of the lens or the stop. Therefore, the groove has a shape as shown in FIG.

(B) An SiO ₂ film 4 was deposited on the entire surface by PE-CVD which is an insulating film with good coverage. The film thickness is ＋ of the groove width A + α, and α is 10 to 100% of 溝 of the groove width A depending on the location.

Since the end of the groove width is filled from the side surface by the SiO ₂ film 4, the groove has an acute angle end 21 of about 10 °. In the present embodiment, a 0.8 μm SiO ₂ film 4 is used.
Is deposited to fill a groove having a width of 1 μm, and the end thereof is formed at an acute angle.

(C) An a-Si film 31 was deposited on the entire surface of the substrate.

(D) The a-Si film other than the groove was removed by chemical mechanical polishing (CMP) so that a-Si was present only in the groove.

Hereinafter, the description will move to FIG.

(E) The a-Si film 31 was turned into a single crystal c-Si film 33 by irradiating a beam of laser along the direction of the groove from the acute end 21 of the groove. At this time, since the amorphous silicon exists only in the groove in advance, it goes without saying that the molten silicon does not flow onto the substrate.

(F) A gate insulating film 5 was formed on the c-Si film.

(G) A gate electrode 6 was formed on the gate insulating film.

(H) The source / drain regions 7, the contact holes 8 and the wirings 9 were formed by a normal TFT manufacturing process to obtain a TFT.

FIG. 5 shows a state in which a-Si in a groove 2 formed on a wide substrate 1 according to a pattern is sequentially annealed by scanning with a laser beam 10.

As shown in this drawing, in many cases, a large number of grooves are formed in a substrate in a vertical and horizontal direction.

By the way, the laser irradiation area or the beam area is much smaller than that of the substrate due to the output of the oscillation source and the optical system. For this reason, as shown in FIG. 5, for example, scanning is performed at a constant speed from the upper left end of the base to the upper right end, then the position is lowered by one step, and scanning is performed at a constant speed from the right end to the left end. By irradiating to the lowermost end, the entire substrate is irradiated.

As can be clearly understood from this figure, the acute angle at both the left and right ends of the groove means that it is unclear whether the light is emitted from the left or right for convenience of scanning, or the light may be emitted from either the left or right. It depends on what you do.

FIG. 6 and FIG. 7 are views for explaining how the a-Si film 5 in the groove is recrystallized by laser annealing.

Although both of these figures should originally be made of one leaf, they are made of two leaves because of the size of the paper.

As shown in (a) to (e), annealing is performed while sequentially moving the laser irradiation region 10 from one acute angle end (left end in the figure) to the other acute angle end (same right end).

At this time, the a-Si
The film 31 is heated by the laser and becomes silicon 35 in a molten state. However, since the laser irradiation area sequentially moves to the right, cooling starts at the same time as the laser irradiation stops.

[0100] The cooling starts first at the leftmost acute corner where the irradiation is started and ended first. Then, the silicon in the molten state is cooled in this portion to precipitate silicon crystals, and the left end is an acute angle, and is a narrow region. For this reason, the first crystallization occurs only at one place. This is shown in FIG. In (c), one fine crystal 36 is formed at the left end of the acute angle.

The cooling and crystallization of the silicon in the molten state is based on the same mechanism and principle as the supercooled water molecules in the air are liquefied by dust and the like in the air as nuclei (see FIG. 1). As shown in FIG. 12A, even when a very small number of molecules form the particle 121, the shape of the particle 121 is convex because the surface such as a sphere is convex and the surface of the particle is concave compared to the plane 122.
The force of sequentially capturing the molecules 124 around 3 is weak. Therefore, crystallization does not occur at a mere melting point. ) This is the interface with the already crystallized part. Therefore, when the laser beam moves to the right end side and is successively crystallized by radiation from the left end side and heat transfer to the glass substrate, newly deposited silicon atoms are to be deposited according to the fine crystals generated at the left end. Become. (Besides the above, due to the difference in thermal conductivity between silicon and silicon dioxide (the former is large), the part surrounded by silicon dioxide may be difficult to cool.) The line is symmetrical in both directions. Therefore, the arrangement of Si or the direction of bonding is likely to be vertical and horizontal. This situation is shown in FIG. In this figure, it can be seen that the heat 11 escapes along the linear wall 24 of the groove, and that the silicon is arranged in order from the left. As a result, the fine crystal grows greatly from the left end to the right end.

As a result, as shown in FIGS. 7D and 7E, the a-Si film was changed to a single crystal silicon film (c-Si) 3.
7 is possible.

After all, in the present embodiment, as shown in FIG. 8, the a-
By sequentially performing laser annealing on the Si film 31, a plurality of single-crystal silicon regions 37 arranged in one horizontal row can be formed. The same applies to the case where these rows are arranged in multiple stages in the vertical direction.

On the other hand, if the leftmost end of the groove is not acute, silicon is inevitably precipitated at a plurality of locations at one end where cooling has started, and a plurality of fine crystals 36 are formed. In this state, precipitation occurs sequentially, so that a large number of (non-huge) crystals 38 each having a narrow width grow one by one according to the crystal orientation (microscopically, a plane) of each initial fine crystal. It will go.

This situation is shown in FIGS. 9A to 9C.
Therefore, in this case, a high-quality semiconductor cannot be obtained.

Although one fine crystal is generated, in an experiment, it depends on the base material, film thickness, etc.
350 nJ / cm ² , 300 in Torr H ₂ atmosphere
Irradiation under the condition of about Hz seems to be preferable.

Further, even if a portion that is not single-crystallized is formed, the crystal itself becomes large, which is much better than the conventional one.

As described above, in the present embodiment, the left and right ends of the groove are both acute angles. However, if the direction of movement of the laser beam is known in advance, only one end where laser irradiation is started may be acute. Of course it is good.

In the formation of the transistor, an acute portion may inevitably cause an undesirable phenomenon such as concentration of an electric field. Therefore, the silicon at the acute portion is removed or is not used even if it is left as it is. It is good to keep it in a state.

The unnecessary ends of the grooves may be filled with an insulator.

(Second Embodiment) FIG. 10 is for explaining a second embodiment of the method of manufacturing a thin film transistor according to the present invention.

In this figure, (a) is a plan view of the groove 22 as viewed from above (irradiation direction). The groove has an elongated, generally rectangular shape that is continuous in the long side direction of the plurality of active regions, and that is uneven. The active region 34 which is the concave portion
The width D of the groove between them is smaller than the width W of the short side of the active region serving as the projection, and the minimum width is 0.1 μm.

Based on the above, after forming an a-Si film in the entire groove as in the previous embodiment, the nuclei are sequentially formed from the left end to the right end as shown in FIG. When laser annealing is sequentially performed under the condition that a fine crystal of .1 μm or more can be formed, a single silicon crystal is formed in a region having a narrow groove width, and in a subsequent active region, crystal growth following the single fine crystal is performed. Occurs.

Therefore, the entire active region can be monocrystallized.

Although not shown in the figure since it is a well-known technique, after dividing the c-Si film in the groove into respective active regions by patterning, a TFT is formed through a normal process to form a TFT. By performing the necessary wiring and the like, a transistor circuit for a liquid crystal display screen is manufactured.

(Third Embodiment) FIG. 11 is a view for explaining a third embodiment of the method of manufacturing a thin film transistor according to the present invention.

(A) of this figure is a plan view seen from above a long and narrow rectangle having a groove width of 2 μm or less. Note that, in the pixel portion and the driving portion of the liquid crystal display panel, the number of these grooves is
Transistors are arranged side by side in many stages, but this corresponds to this. For this reason, it is needless to say that these grooves (rows) are actually formed side by side.

As shown in (b) of the figure, the laser beam is moved from the left end to the right end in accordance with the solidification speed of the molten silicon by cooling, and laser annealing is performed in this order. Are formed with a plurality of fine crystals, and then these fine crystals grow respectively to form crystal grain boundaries. However, as the annealing region moves further to the right, the groove width E becomes, for example, 2 μm to a certain value. When the grain size is small, the grain grown first becomes dominant under a slight difference in the growth of each grain boundary, and as a result, it becomes a single crystal from a place several tens to several hundreds μm away from the starting point of precipitation. . (Therefore, the groove is formed up to a wide area extending several hundred μm to the left and right from the original transistor mounting area.) Then, since it is a well-known technique, it is not shown in the drawing. After the c-Si film in the trench is divided into the respective active regions by the thinning, a normal process is performed except for removing a portion where the leftmost crystal is not single-crystallized.
FT will be formed.

In this embodiment, both ends of the groove may have acute angles.

(Other Embodiments) 1) In the case where one transistor and one transistor have a small groove, FIG.
(A), the groove has a trapezoidal shape in which the irradiation start end is inclined, and the laser beam also has a trapezoidal shape in which the end is inverted. As a result, a sharper angle is formed at the end of the laser beam irradiation, and a fine crystal 36 is formed.

2) As shown in FIG. 13B, the amorphous silicon is slightly raised on the base. In this way, the molten silicon does not flow to the substrate surface in the molten state, but further radiative heat removal from the molten silicon exposed on the substrate and present at the end, thereby forming fine nuclei. .

3) At the sharp end of the groove, a heat dissipating metal piece 12 is placed to rapidly cool the molten silicon. Since this metal piece is unnecessary as a transistor, it is needless to say that the metal piece is removed in any of the steps during manufacturing.

Although the present invention has been described based on several embodiments, it goes without saying that the present invention is not limited to these embodiments. That is, for example, the following may be performed.

1) For convenience of equipment, etc., one component (requirement) of the present invention is made plural, or conversely, plural components are integrated.

2) Depending on the development of the technology in the future and the material of the base, the grooves are formed by other means such as mechanical means, melting by a strong laser, and scattering.

Alternatively, they are formed in a single step.

3) The semiconductor to be giant crystallized is a substance other than silicon, for example, Si-Ge, Si-Ge-C, or the like.

Similarly, the base is made of another material such as silicon.

In these cases, the optimum conditions for the generation of one fine crystal serving as a nucleus of a large crystal are determined based on a rough examination according to the material, an experiment with trial and error, and the like. Needless to say, it is appropriately set.

4) The depth of the groove is 200 nm or less, preferably about 50 nm (40
６０60 nm), but for some reason 300
μm or more.

5) In the formation of a groove having irregularities, the depth of the groove may be different from that of the concave or convex depending on the working method and the forming method, such as simple patterning, changing the size of the focal point by moving the lens up and down, and the like. It is different from the department.

Further, both sides (upper and lower sides in the figure) of the active region are parallel to facilitate the growth of a single crystal.

6) The cross section of the linear groove is V-shaped, U-shaped or the like depending on the working and forming method.

[0134]

As described above, according to the present invention, silicon or polysilicon made of amorphous silicon or fine crystals is converted into single crystal silicon by laser annealing or silicon made of a larger crystal than conventional ones. It becomes possible. For this reason, a TFT using a single crystal silicon film or a giant crystal silicon film in the active region can be manufactured. As a result, uniform and stable characteristics and higher mobility can be achieved as compared with the case of using the silicon film of the related art.

The liquid crystal display device which uses these crystals, this silicon, or a transistor for a circuit for designating a location of an active matrix, a shift register for a signal to be sent to each TFT, and the like, also has excellent performance. Become.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic procedure of a conventional method for manufacturing a thin film transistor.

FIG. 2 is a diagram conceptually showing a crystalline state of polysilicon in a conventional method of manufacturing a thin film transistor.

FIG. 3 is a diagram illustrating a method of manufacturing a thin film transistor according to a first embodiment of the present invention.
FIGS. 4A and 4B are a plan view and a cross-sectional view illustrating a state in which a transistor is formed in accordance with a manufacturing process.

FIG. 4 is a diagram paired with FIG. 3;

FIG. 5 is a diagram showing a state in which silicon on a substrate is sequentially annealed with a laser from the upper left end to the lower right end in the first embodiment.

FIG. 6 is a diagram similar to FIG. 7 in the first embodiment.
FIG. 9 is a diagram for explaining the reason why the irradiation start end of the groove is formed at an acute angle in combination with FIG.

FIG. 7 is a diagram paired with FIG. 6;

FIG. 8: aS in a number of grooves arranged in a row on the base
It is a figure which shows a mode that a laser beam scans and anneals in order.

FIG. 9 is a diagram showing a state of silicon crystal growth in a case where the end of the groove is not an acute angle, in order to explain the principle, effect, and operation of the first embodiment.

FIG. 10 is a drawing for explaining a second embodiment of the method for manufacturing a thin film transistor according to the present invention.

FIG. 11 is a diagram for explaining a third embodiment.

FIG. 12 is a diagram for explaining the principle that silicon is aligned and solidified from a solid surface.

FIG. 13 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 2 Groove of substrate 20 Slender end of groove 21 Sharp end of groove 22 Slender groove with unevenness 23 Slender rectangular groove 24 Linear wall of groove 31 a-Si film 32 p-Si film 33 c-Si film 34 active region 35 molten Si 36 microcrystal 37 silicon crystal film 38 non-large silicon crystal 4 SiO ₂ film 5 gate insulating film 6 gate electrode 7 source / drain region 8 contact hole 9 wiring 10 laser irradiation region (beam) 11 Heat that escapes (flows) to the outside 12 Metal pieces for heat dissipation

Claims (14)

[Claims] 1. A groove forming step of forming a groove having an acute angle of not more than 30 ° at the end of laser irradiation for laser annealing in at least an active region of a transistor on a substrate; A method of manufacturing a thin film transistor, comprising: a step of embedding a semiconductor to be annealed for filling a semiconductor made of a microcrystal or the like; and an annealing step of turning a semiconductor to be annealed in the trench into a large crystal semiconductor by laser annealing. 2. The thin film transistor according to claim 1, wherein the groove forming step is a sharp angle forming step in which the acute angle of the first end of the laser irradiation for the laser annealing is set to 15 ° or less. Manufacturing method. 3. The groove forming step according to claim 1, wherein the groove forming step is a groove independent forming step of forming the grooves independently at least for each region to be an active region of each thin film transistor. 3. The method for manufacturing a thin film transistor according to item 1. 4. The groove forming step includes: a temporary groove forming small step of temporarily forming a temporary groove in which the first end portion of the laser irradiation is not necessarily at an acute angle using a photolithography technique; _{3. The method according} to claim 1, further comprising an acute angle forming small step of forming an SiO ₂ film having a thickness of 55% or more of the temporary groove width on the temporary groove.
Alternatively, the method for manufacturing a thin film transistor according to claim 3. 5. A structure in which at least a portion of a substrate is continuously connected to a long side direction of an active region of a thin film transistor, and a groove width of a portion other than the active region is narrower than a short side of the active region. Forming a concave / convex existing groove so that the minimum groove width is 0.2 μm or less; embedding a semiconductor to be annealed to fill a semiconductor made of amorphous, fine crystal or the like in the premises where the concave / convex exists; An annealing step of performing laser irradiation for turning a semiconductor to be annealed in the premises into a large crystalline semiconductor by laser annealing from one end of the groove having the unevenness along the groove. . 6. The surface of a film according to claim 5, wherein the step of forming a concave / convex existing groove has a small step of forming an acute-angle groove for forming a laser irradiation start end side for annealing at an acute angle. Purification method. 7. A groove forming step of forming a groove having a width of 2 μm or less in at least a long side direction of an active region of a thin film transistor on a substrate, and annealing for filling a semiconductor made of amorphous, fine crystal or the like in the groove. Manufacturing a thin film transistor, comprising: a target semiconductor embedding step; and an annealing step of sequentially performing laser irradiation along the groove to turn the annealing target semiconductor in the groove into a large crystalline semiconductor by laser annealing. Method. 8. The method according to claim 7, wherein the groove forming step includes a small step of forming an acute angle groove for forming a laser irradiation start end side for annealing at an acute angle. . 9. The step of burying a semiconductor to be annealed includes: a small step of depositing a semiconductor to be annealed for depositing a semiconductor made of amorphous, fine crystal or the like over the entire surface of the substrate; and a small step of removing a semiconductor deposited at an unnecessary portion. The method for manufacturing a thin film transistor according to claim 1, wherein the method includes the steps of (a), (b), (c), (c), and (d). 10. An annealing target semiconductor selection step of selecting at least one of amorphous silicon and silicon made of fine crystals having a grain size of 0.1 μm or less as a semiconductor to be embedded and annealing, prior to the annealing target semiconductor embedding step. 10. The method of manufacturing a thin film transistor according to claim 1, wherein the thin film transistor is formed by a method as defined in claim 1, 2, 3, 4, 5, 6, 7, 8, or 9. 11. A substrate on which a thin film transistor is formed, comprising: a groove having at least one end having an acute angle of 30 ° or less; and a large crystalline semiconductor in the groove. Substrate. 12. A substrate on which a thin film transistor is formed, wherein the substrate has a shape continuously connected to a long side direction of an active region of the thin film transistor, and a groove width of a portion other than the active region is smaller than that of a short side of the active region. And the minimum width is 0.
A substrate on which a thin film transistor is formed, comprising: a groove of 2 μm or less; and a large crystalline semiconductor in an active region in the groove. 13. A substrate on which a thin film transistor is formed, wherein a linear groove having a width of 2 μm or less continuously connected to a long side direction of an active region of the thin film transistor, and a large crystal of the active region in the groove. A substrate on which a thin film transistor is formed, comprising a semiconductor. 14. The substrate according to claim 13, wherein at least one end of the groove has an acute angle of 30 ° or less.