JP2000068203A - Polycrystalline silicon formed by crystallization of microcrystalline silicon and its forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a thin film transistor semiconductor film composed of polycrystalline silicon formed by crystallization of microcrystalline silicon. SOLUTION: A method which forms a polycrystalline silicon film from a microcrystal silicon film includes a step of depositing a microcrystalline silicon film 14 including microcrystallites buried in amorphous substance, a step of annealing the deposited film 14 and, at least, partially forming a polycrystalline film, and a step of promoting formation of uniform crystal particles 28, 30 having comparatively large size by allowing the amorphous substance to contain buried seed crystals 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates generally to thin film transistor (TFT) processes and fabrication, and more particularly, to a polycrystalline film formed from a microcrystalline film and a method of forming the polycrystalline film.

[0002]

2. Description of the Related Art The demand for smaller electronic appliances with higher resolution displays has spurred continued research and research in the liquid crystal display (LCD) field. Large-scale integrated (LSI) driver circuits and ultra-large-scale integrated circuits (VL) currently provided around LCDs
By incorporating the SI) driver circuit in the LCD, the size of the LCD can be reduced and the performance is improved. Eliminating external driver circuits and transistors reduces product size, reduces process complexity, and reduces the number of process steps, resulting in LCDs
The price of products equipped with is reduced.

[0003]

A major component of the LCD, and a component that needs to be improved for further progress of the LCD, is a thin film transistor (TFT). Usually, the TFT is mounted on a transparent substrate such as quartz or glass. By increasing the electron mobility in the device, T
FT performance is improved. When electron mobility increases, LCD
The brightness of the screen is increased, the power consumption is reduced, and the transistor response time is faster. Many of these features for performance improvement are due to the improvement in switching characteristics of the TFT. In addition, average TFT performance is required to further improve the LCD. That is, the display and all driver transistors in the display must operate at substantially the same level of performance.

[0004] Transistors formed from amorphous silicon have low carrier mobilities and are insufficient for LCD driver circuits. The carrier mobility of the transistor is improved by using crystallized silicon. In order to make the transistor performance uniform, it is necessary that the crystal film for forming the TFT has a uniform crystal structure over a wide area. Preferably, the crystal film for forming the TFT semiconductor is crystallized into one uniform crystal pattern. This uniform pattern, or single crystal structure, ensures that all transistors in the film have the same performance characteristics. However, single crystal silicon films used with LCDs are difficult to manufacture when bonded to relatively fragile transparent substrates. A polycrystalline film lies between a single crystal film having excellent performance and amorphous silicon having poor performance. Usually, a polycrystalline film has a plurality of crystal regions that are adjacent but have different crystal orientations. That is,
The film is composed of many different crystalline regions having irregular shapes and irregular crystal orientations. Uniform performance across the polycrystalline film is improved by making the crystalline regions or grains as large as possible.

[0005] By obtaining uniform crystallization over a wide area inside the polycrystalline film, it is ensured that the performance of each specific crystal grain is uniform. In addition, the performance of transistors made from polycrystalline films can be improved by reducing the number of grain boundaries or reducing the area of intersection between different crystal grains. The grain boundary region between crystal grains is TF
An electron trap that lowers the electron mobility during T is formed. Consequently, device stability decreases with increasing threshold voltage and leakage current of such devices.

Forming a polycrystalline film having large particles,
That is, one problem in forming an improved TFT is that
It is necessary to use an amorphous material as a building block. Another problem is that the glass substrate and the quartz substrate on which the TFT is formed have a relatively low heat-resistant temperature. Usually, the transparent substrate is covered with a film of an amorphous material such as silicon or a silicon-germanium compound. When the amorphous material is heated or annealed, the amorphous material becomes crystalline. Typically, the anneal process is limited by the requirement that the amorphous material cannot be heated above about 600 ° C. If the temperature exceeds 600 ° C., the transparent substrate is often damaged.

There are various annealing methods for converting amorphous silicon to polycrystalline silicon. Solid phase crystallization (SPC) is a popular method for crystallizing silicon in a heating furnace. In this process, the amorphous silicon is converted for at least several hours.
It is exposed to heat near 600 ° C. Typically, heat is generated from a resistive heater heat source. Rapid thermal annealing (R
TA) uses higher temperatures, but for a very short time. Typically, during the annealing process, the substrate
Heated at a temperature between 00C and 500C, the amorphous film and the transparent substrate are placed on a surface or susceptor heated to a relatively low temperature. In this manner, silicon can be used without degradation of the transparent substrate on which the film is placed.
It is heated to a temperature between 00C and 800C. One method of performing this annealing is to use ultraviolet light from a heat lamp such as a halogen heat lamp.

Excimer laser crystallization (ELC) processes have shown some success in annealing amorphous silicon. The laser allows regions of the amorphous film to be exposed to very high temperatures for a very short time. In theory, this offers the possibility to anneal the amorphous silicon at the optimal temperature without degrading the transparent substrate on which the amorphous silicon is deposited.
However, the use of this method has been limited due to a lack of control over some process steps. Usually, the laser aperture size is relatively small. Given the aperture size, laser power, and film thickness, multiple laser paths or laser shots are required, ultimately annealing the silicon. Since it is difficult to control the laser accurately, using multiple shots causes variations in the annealing process.

[0009] The process of heating amorphous silicon to form crystallized silicon is not fully understood and research on that subject is ongoing. Various factors affect the annealing of amorphous silicon, such as temperature, film thickness, degree of melting of the amorphous material, impurities in the film, and a range of other factors. Usually, crystallization of the largest particles occurs at a specific temperature near the melting point in the polycrystalline film. At temperatures below this preferred temperature, the amorphous silicon is not melted enough to form a large grain area. At temperatures above the preferred temperature, bulk nucleation (bulk)
causes rapid nucleation). Bulk nucleation of amorphous materials results in relatively small particle sizes.

The method of depositing amorphous silicon on a transparent substrate is also important in the production of a polycrystalline film having large crystal grains. Usually, a transparent substrate is provided on a heated susceptor. The transparent substrate is exposed to a gas containing a silicon element and a hydrogen element. The gas decomposes, leaving solid phase silicon on the substrate. Plasma CVD
In (PECVD) systems, the use of radio frequency (RF) energy aids in the decomposition of the source gas. Low pressure CVD
(LPCVD) system or ultra-high vacuum CVD (UHV)
-CVD system pyrolyzes the source gas at low pressure. In a photo-CVD system, photon energy aids in the decomposition of the source gas. In high density plasma CVD systems, high density plasma sources such as inductively coupled plasmas and helicon sources are used. In a hot wire CVD system, source gas is decomposed by generation of active hydrogen atoms.

It would be advantageous if the grains of the annealed polycrystalline film could be made larger (on the order of 10 microns). Since a plurality of active elements can be formed on such a large particle, the same effect as that of a single crystal film can be obtained partially.

It would be advantageous if the grain size in the polycrystalline film could be made uniform so as to minimize the differences between the grains in the film, ie, to minimize the differences between active elements in different grain regions.

It would be advantageous if the grain regions of the polycrystalline film could be manufactured to have the same crystallographic orientation to minimize differences between TFTs in adjacent grains in the film.

It would be advantageous if a process could be devised that made the process of annealing the polycrystalline film less dependent on variations in the amorphous film deposition process and the process of heating and crystallizing the amorphous film.

[0015]

SUMMARY OF THE INVENTION A method of forming a polycrystalline film from a microcrystalline film according to the present invention comprises the steps of: a) depositing a microcrystalline film including microcrystalline embedded in an amorphous material; Annealing the film deposited in step a) to form an at least partially polycrystalline film, thereby having a relatively large size by including an embedded seed crystal in an amorphous material Promoting the formation of uniform crystalline particles.

The microcrystalline film deposited in the step a) has two thicknesses, that is, a predetermined first thickness and a predetermined second thickness covering the first thickness; Step b) comprises the step of melting the second thickness of the film, whereby a controlled number of seed crystals within the thickness of the first film cause the formation of uniform, large-sized crystal grains. May be promoted.

The step b) includes heating the microcrystalline film deposited in the step a) so as to selectively melt the amorphous material, wherein a predetermined number of microcrystallites in the amorphous material are used. It may remain unmelted, so that a controlled number of seed crystals may promote the formation of uniform, large-sized crystal grains.

[0018] Subsequent to step a), the method further comprises the step of depositing a second completely amorphous film covering the microcrystalline film deposited in step a), wherein the annealing in step b) is performed. Increasing the crystalline region from the microcrystalline film into the second film may include the step of making the film deposition process faster with the use of a completely amorphous film.

The microcrystalline film has a predetermined first thickness;
The second film has a predetermined second thickness, the second thickness typically being less than about 25% of the combined thickness of the first thickness and the second thickness. There may be.

The step a) includes the step of embedding the microcrystallite in the amorphous material, usually at a density of less than 10 ⁻⁸ cm ⁻² , whereby the distribution and the size of the crystal grains are reduced within the microcrystalline film. It may be adjusted according to the number of seed crystals.

The step a) is usually performed at 50 ° to 500 °.
Depositing a film comprising an amorphous material embedded microcrystallites having a size in the range of Å, whereby control over the size and stability of the crystal mass may be responsive to the size of the seed crystal .

The amorphous substance and the microcrystallite of the film deposited in the step a) may be silicon.

[0023] The amorphous substance and the microcrystallite of the film deposited in the step a) may be a silicon-germanium compound.

Step a) includes depositing a film in which the microcrystallites embedded in the amorphous material have a uniform distribution pattern, thereby minimizing the number of grain boundaries. May be.

The step a) is substantially the first predetermined step.
Depositing a microcrystalline film embedded with microcrystallites having a crystallographic orientation of: wherein said step b) comprises microcrystallites of said first crystallographic orientation deposited in said step a) Annealing the polycrystalline film may include minimizing grain boundaries by using the same crystallographic orientation throughout the polycrystalline film.

[0026] The first crystal orientation of the embedded microcrystallite may be (110).

The step b) heating the microcrystalline film deposited in the step a) so as to selectively eliminate microcrystallites having no predetermined first crystal orientation; Annealing the microcrystalline film to have the remaining microcrystalline of the first crystallographic orientation, such that having the same crystallographic orientation throughout the polycrystalline film minimizes grain boundaries. It may be.

[0028] The first crystal orientation of the embedded microcrystallite may be (110).

[0029] Step b) may include annealing the film deposited in step a) with an excimer laser crystallization (ELC) process in which the film is heated with light having a wavelength of about 308 nm or less.

[0030] The step b) may include annealing the microcrystalline film deposited in the step a) at a temperature near the melting point of the amorphous material for about 50 nanoseconds.

The microcrystalline film deposited in the step a) is silicon, and the step b) is usually performed at 900 ° C.
The method may include annealing the microcrystalline film at a temperature in the range of １1600 ° C.

The microcrystalline film deposited in step a) is silicon-germanium, and the step b)
May typically include annealing the microcrystalline film at a temperature above 800 ° C.

The step b) includes a step of annealing the microcrystalline film deposited in the step a) by a heating furnace annealing process in which the microcrystalline film is heated at a temperature of less than about 600 ° C. for a period usually ranging from 3 hours to 3 days. May be included.

The step b) is a rapid thermal annealing (RTA) crystallization process in which the microcrystalline film deposited in the step a) is heated at a temperature of less than about 900 ° C., usually for 1 to 5 seconds. An annealing step may be included.

The step a) may include depositing a microcrystalline film having a thickness of less than about 1000 °, so that the polycrystalline film is suitable for manufacturing a thin film transistor.

Step a) may include depositing a microcrystalline film having a thickness of less than about 500 °, so that the polycrystalline film is well suited for the manufacture of thin film transistors.

The step a) may include the step of depositing the microcrystalline film by a PECVD process using a mixed gas of SiH ₄ and H ₂ .

The microcrystalline film is treated in step a) at a power level of about 600 W, a temperature of about 320 ° C., a total pressure of about 1.2 Torr, a SiH ₄ flow rate of 20 sccm and a H ₂ flow rate of 2000 sccm. May be deposited.

In the step a), the microcrystalline film is formed by low pressure CVD (LPCVD), ultrahigh vacuum CVD, light C
It may be deposited by a process selected from the group consisting of VD, high density plasma CVD, hot wire CVD, and sputtering.

The microcrystalline film is used in the step a).
And disilane (Si_TwoH₆), Formula Si _NH_{2N + 2}(N> 2)
Higher order silanes represented by
_NH_{2N +2}/ Si_NF_{2N + 2}Sila represented by (N ≧ 1)
Selected from the group consisting of chemical mixtures of
It may be deposited by a selected chemistry.

The step a) may include depositing the microcrystalline film in an ultra-high vacuum, thereby improving microcrystalline formation by minimizing contaminants.

The polycrystalline film is formed so as to cover a transparent substrate, and the step a) includes depositing the microcrystalline film on the transparent substrate, whereby the polycrystalline film is formed on a liquid crystal display ( It may be suitable for manufacturing a thin film transistor for LCD).

The step a) includes a step of cleaning the transparent substrate before depositing the microcrystalline film, so that the formation of microcrystallite in the microcrystalline film is promoted. Is also good.

[0044] The transparent substrate may be selected from the group consisting of quartz, glass, and plastic.

The method of forming a thin film transistor comprising a polycrystalline film on a transparent substrate from a substantially amorphous film according to the present invention comprises the steps of: a) transforming microcrystallite into amorphous with a density of usually less than 10 ⁻⁸ cm ^−2; Embedding in a silicon material, wherein the microcrystallites typically have a size of 50 ° to 500 ° to form a microcrystalline material; b) converting the microcrystalline material of step a) to SiH ₄ and H PEC using mixed gas of ₂
Approximately 600W power level, 320 ° C in VD process
Temperature, about 1.2 Torr total pressure, 20 sccm Si
Depositing on said transparent substrate under conditions of H ₄ flow rate and H ₂ flow rate of 2000 sccm; c) from said microcrystalline material deposited in said step b), a total thickness of about 5
Forming a film to be less than 00 °; d)
Heating the film deposited in step a) with light having a wavelength of less than about 308 nm in an ELC process; e) increasing the thickness of the second film at a temperature typically in the range of 900 ° C to 1600 ° C. Melting for nanoseconds to form an at least partially polycrystalline film, thereby promoting the formation of uniform crystalline particles having a relatively large size by including seed crystals in the amorphous material. A method is provided that includes:

Liquid crystal display (LCD) according to the present invention
Is a transparent substrate and a TFT polycrystalline semiconductor film. The semiconductor film covers the transparent substrate, and deposits a microcrystalline film containing an amorphous substance in which microcrystallite is embedded on the substrate. A liquid crystal display comprising: a semiconductor film formed by annealing a crystalline film, thereby promoting formation of uniform crystalline particles having a relatively large size by including a seed crystal embedded in the amorphous material. Is provided.

The deposited microcrystalline film has two thicknesses, that is, a predetermined first thickness and a predetermined second thickness covering the first thickness, and the microcrystalline film is annealed. Melting the thickness of the second film so that a controlled number of the seed crystals within the thickness of the first film causes the formation of uniform, large-sized crystal grains. You may make it promote.

The microcrystalline film is heated to selectively melt the amorphous material, and a predetermined number of the microcrystallites remain unmelted in the amorphous material, thereby providing a controlled number of the microcrystallites. The seed crystal may promote the formation of uniform and large-sized crystal particles.

[0049] The method further comprises a second film of completely amorphous material overlying the microcrystalline film, wherein the annealing step expands a crystalline region from the microcrystalline film into the second film, whereby the The use of a completely amorphous film may speed up the film deposition process.

The microcrystalline film has a predetermined first thickness,
The second film has a predetermined second thickness, the second thickness typically being less than about 25% of the combined thickness of the first thickness and the second thickness. There may be.

The microphone embedded in the microcrystalline film
Locrystalite density is usually 10 ^-8cm^-2Less than
As a result, the distribution and size of crystal grains
Adjusted according to the number of the seed crystals in the crystal film
Is also good.

The microcrystalline film is embedded with the microcrystallites, usually having a size in the range of 50 ° to 500 °, so that control over the size and stability of the crystal mass is responsive to the size of the seed crystal. You may.

The amorphous material and the microcrystallite of the microcrystalline film may be silicon.

[0054] The amorphous substance and the microcrystallite of the microcrystalline film may be a silicon-germanium compound.

The microcrystallite embedded in the amorphous material may have a uniform distribution pattern, thereby minimizing the number of grain boundaries.

The microcrystallite embedded in the microcrystalline film has a substantially predetermined first crystal orientation, and the polycrystalline film has microcrystallite of the first crystal orientation; Thereby, grain boundaries may be minimized by using the same crystal orientation throughout the polycrystalline film.

[0057] The first crystal orientation of the embedded microcrystallite may be (110).

The microcrystalline film is selectively heated so as to eliminate microcrystallites having no predetermined first crystal orientation, and substantially remaining microcrystallites change the first crystal orientation. The microcrystalline film may be annealed to have the same crystallographic orientation throughout the polycrystalline film to minimize grain boundaries.

[0059] The first crystal orientation of the embedded microcrystallite may be (110).

[0060] The microcrystalline film may be annealed in an excimer laser crystallization (ELC) process using light having a wavelength of about 308 nm or less.

[0061] The microcrystalline film may be annealed at a temperature near the melting point of the amorphous material for about 50 nanoseconds.

[0062] The microcrystalline film may be silicon, and the microcrystalline film may be annealed at a temperature usually in the range of 900 ° C to 1600 ° C.

[0063] The microcrystalline film may be silicon-germanium, and the microcrystalline film may be annealed at a temperature usually exceeding 800 ° C.

The microcrystalline film may be annealed in a furnace annealing process at a temperature below about 600 ° C. for a period typically ranging from 3 hours to 3 days.

The microcrystalline film may be annealed in a rapid thermal anneal (RTA) crystallization process, typically at a temperature below about 900 ° C. for a period in the range of 1-5 seconds.

The microcrystalline film may have a thickness of less than about 1000 °, so that the polycrystalline film is suitable for manufacturing a thin film transistor.

[0067] The microcrystalline film may have a thickness of less than about 500 °, so that the polycrystalline film is very suitable for the manufacture of thin film transistors.

The microcrystalline film may be deposited by a PECVD process using a mixed gas of SiH ₄ and H ₂ .

The microcrystalline film has a power level of about 600 W, a temperature of about 320 ° C., a total pressure of about 1.2 Torr,
It may be deposited under conditions of a SiH ₄ flow rate of sccm and a H ₂ flow rate of 2000 sccm.

The microcrystalline film is formed by low pressure CVD (LPCV).
D), ultra-high vacuum CVD, optical CVD, high-density plasma CV
It may be deposited by a process selected from the group consisting of D, hot wire CVD, and sputtering.

The microcrystalline film is made of disilane (Si ₂ H ₆ ),
Formula Si _N H _2N + 2 higher order silane from represented by (N> 2), and the structural formula _{Si N H 2N + 2 / Si} N F 2N + 2 (N ≧
It may be deposited by a chemistry selected from the group consisting of a silane / fluorosilane chemical mixture represented by 1).

The microcrystalline film may be deposited in an ultra-high vacuum environment, thereby enhancing the formation of the microcrystallite by minimizing contaminants.

[0073] The transparent substrate may be washed before the microcrystalline film is deposited, thereby promoting the formation of the microcrystallite in the microcrystalline film.

[0074] The transparent substrate may be selected from the group consisting of quartz, glass, and plastic.

A method for forming a polycrystalline film from a microcrystalline film, comprising: a) depositing a microcrystalline film containing microcrystallite embedded in an amorphous material; b) the film deposited in step a) Annealing to form an at least partially polycrystalline film. The inclusion of the embedded seed crystal in the amorphous material facilitates the formation of uniform crystal grains having a relatively large size.

In another aspect of the invention, step a)
Has two thicknesses, namely, a first predetermined thickness and a second predetermined thickness covering the first thickness. Step b) includes melting the second thickness of the membrane. A controlled number of seed crystals within the thickness of the first film facilitate the formation of uniform, large-sized crystal grains.

In another aspect of the invention, step b)
Includes heating the microcrystalline film deposited in step a) to selectively melt the amorphous material, such that a predetermined number of microcrystallites in the amorphous material remain unmelted. A controlled number of seed crystals promotes the formation of uniform, large-sized crystal grains.

In another aspect of the invention, the process further comprises, following step a), depositing a second film of completely amorphous material overlying the microcrystalline film deposited in step a). Annealing in step b) includes expanding the crystalline region from the microcrystalline film into the second film. The film deposition process is faster with the use of a completely amorphous film. Preferably, the microcrystalline film has a predetermined first thickness, and the second film has a predetermined second thickness. The second thickness is typically less than about 25% of the combined thickness of the first and second thicknesses.

In yet another aspect of the present invention, step a) comprises the step of embedding microcrystallites in an amorphous material, typically at a density of less than 10 ^-8 cm ^-2 . The distribution and size of the crystal grains are adjusted according to the number of seed crystals in the microcrystalline film. Step a) also includes the step of depositing a film comprising an amorphous material embedded with microcrystallites having a size typically in the range of 50-500 °. Control over crystal size and stability is responsive to seed crystal size.

In a preferred embodiment, the amorphous material and microcrystallite of the film deposited in step a) are silicon. In another aspect of the invention, the amorphous material and the microcrystallite of the film deposited in step a) are silicon-germanium compounds.

A liquid crystal display including a transparent substrate and a TFT polycrystalline semiconductor film covering the transparent substrate is provided. TF
The T polycrystalline semiconductor film is formed by depositing a microcrystalline film containing an amorphous substance embedded with microcrystallite on a substrate and annealing the microcrystalline film.
Including a seed crystal embedded in the amorphous film facilitates the formation of uniform crystal grains having a relatively large size.

[0082]

1 through 4 illustrate steps of a method of forming an LCD 10. FIG. Finally, the LCD shown in FIG.
10 includes a transparent substrate 12 and a polycrystalline semiconductor film covering the substrate 12 (see FIG. 4). Usually, the substrate 12 is quartz,
It is selected from the group consisting of glass and plastic.
The polycrystalline film is formed by depositing the microcrystalline film 14 on the substrate 12. The microcrystalline film 14 includes an amorphous material 15 embedded in microcrystallites, ie, small seed crystals 16. The microcrystalline film 14 has a thickness 17. Typically, a barrier layer separates substrate 12 from film 14. (However, it is not shown for easy viewing of the drawing.) In the process of forming the LCD 10, TF
A T device (not shown) is formed from the film 14.

FIG. 2 shows annealing of the microcrystalline film 14 for forming the polycrystalline TFT film shown in FIG. Membrane 14
Arrows 18 pointing perpendicular to the surface of the laser indicate light from an excimer laser (not shown). The laser beam 18 is typically moved along the surface of the film 14 during the annealing process due to the limited aperture size of the laser. The direction of movement of the laser beam 18 is indicated by an arrow 20 parallel to the film 14. A portion indicated by reference numeral 22 of the film 14 indicates a portion melted by the laser beam 18. Normal,
In the melting region 22, a number of microcrystallites melt during the annealing process. The remaining microcrystals 24
This is a seed crystal that forms crystal grains in the melting region 22. In one aspect of the invention, the microcrystalline film 14 is heated such that the amorphous material 22 is selectively melted and a predetermined number of microcrystallites 24 remain in the amorphous material 22 without melting. A controlled number of seed crystals 24 facilitate the formation of uniform, large-sized crystal grains.

FIG. 3 is a partial cross-sectional view of the LCD 10 in the annealing process started with FIGS. The laser beam 18 moves laterally along the film 14 so that the region 26 melts. As the film region 22 cools, crystal grains 28 form around the seed crystal (not shown), and the film region 30 crystallizes to form particles around the microcrystallite 24.

FIG. 4 is a partial sectional view of LCD 10 after the annealing process. Here, the TFT polycrystalline semiconductor film 31 covers the transparent substrate 12. The film 31 is composed of a region of large crystal grains including the grains 28 and 30. Embedding the seed crystal 16 in the amorphous material 15 (see FIG. 1) facilitates the formation of uniform grain crystals 28 and 30 of relatively large size.

FIG. 5 is a partial cross-sectional view of the LCD 10 of FIG. 1 where the deposited microcrystalline film 14 has two thicknesses.
The film 14 has a predetermined first thickness 32 and a first thickness 32.
And a predetermined second thickness 34 covering the second thickness. Annealing the microcrystalline film 14 includes melting the second thickness of the film 34. Selective melting of the film 14 is achieved by varying the overall thickness of the film 14, the energy of the laser beam 18, the irradiation time of the laser beam 18, and the number of repetitions of the irradiation of the laser beam 18. By controlling the thicknesses of the first thickness 32 and the second thickness 34, the number of seed crystals 16 in the first thickness 32 is adjusted. Controlling the number of seed crystals 16 within the first film thickness 32 facilitates the formation of uniform, large-sized crystal grains.

FIG. 6 shows the LCD 1 of FIG. 1 further including a second completely amorphous film 36 covering the microcrystalline film 14.
0 is a partial sectional view. The use of a completely amorphous film 36 speeds up the film deposition process, since a completely amorphous film 36 has relatively little complexity in deposition. That is, the deposition process is faster because the film 36 of a completely amorphous material is easier to deposit. Since the annealing process includes a step of expanding the crystal region from the microcrystalline film 14 to the second film 36, the advantage of using the microcrystalline film 14 is utilized. The microcrystalline film 14 has a predetermined first thickness 38.
And the second film 36 has a predetermined second thickness 40. The second thickness 40 is typically less than about 25% of the combined thickness of the first thickness 38 and the second thickness 40. Investigations are ongoing to increase the second thickness 40 relative to the first thickness 38 to further speed up the deposition process.

Referring to FIG. 1, according to one aspect of the present invention, the density of microcrystals 16 embedded in microcrystal film 14 is typically less than 10 ⁻⁸ cm ⁻² . The distribution and size of crystal grains obtained after the annealing process are adjusted according to the number of seed crystals 16 in microcrystalline film 14. The present invention has been developed to overcome the instability of depositing an amorphous film on a transparent substrate and the non-uniformity of the annealing process, especially when using an excimer laser. Excimer lasers allow for more selective heating of the silicon film, providing additional options in the annealing process. However, also due to the high energy, short irradiation time, and small aperture of the excimer laser beam, a non-uniform annealing process results. The use of microcrystallites 16 in adjusting the annealing process reduces the chemical composition of microcrystalline film 14, the thickness of film 14, and the reliance on variations in the heating and annealing processes.

The annealing process is also adjusted with the size of the microcrystallite 16. Still referring to FIG. 1, the microcrystalline film 14 is embedded with microcrystallites 16 having a size typically in the range of 50 ° -500 °. The size and stability of the crystal mass are controlled according to the size of the seed crystal 16.

In one aspect of the invention, the amorphous material 15 and the microcrystallite 16 are silicon. In another aspect of the invention, the amorphous material 15 and the microcrystalline 16 are silicon-germanium compounds.

Still referring to FIG. 1, the microcrystallite 16 embedded in the amorphous material 15 has a uniform distribution pattern. The number of grain boundaries is minimized when the microcrystallites 16 in the film 14 are arranged uniformly and uniformly.

In one aspect of the present invention, the microcrystalline film 14
Embedded in the microcrystallite 16 has a substantially predetermined first crystallographic orientation. Referring to FIG. 4, the polycrystalline film 31 has the microcrystalline 16 having the first crystal orientation shown in FIG. By using the same crystal orientation throughout the polycrystalline film 31, crystal grain boundaries are minimized. Preferably, embedded microcrystallite 1
The first crystal orientation of No. 6 is (110). In the above process, the crystal orientation of the microcrystallite 16 is
It is determined before the microcrystallite 16 is embedded in the membrane 14. Suitable crystallographic orientations or textures can be obtained by appropriate selection of film deposition conditions. The preferred texture of the deposited microcrystallite is transferred to crystal grains formed after the annealing process.

[0093] In another aspect of the present invention, the microcrystallite 16 is treated with a microcrystalline film 14 prior to annealing.
Have an irregular crystallographic orientation when embedded in The microcrystalline film 14 is selectively heated in order to eliminate the microcrystallite 16 having no predetermined first crystal orientation. The microcrystalline film 14 is annealed such that the microcrystallite 16 having substantially the first crystal orientation remains. Referring to FIG. 4, by setting the same crystal orientation throughout the polycrystalline film 31, a crystal grain boundary is minimized. That is, the heat in the annealing process is selected to melt all crystallites 16 except the crystallite 16 having the first crystallographic orientation. The microcrystallite 16 having the first crystal orientation has a higher melting point than the microcrystallite 16 having the other crystal orientation, and thus remains without being melted even after the annealing process. Preferably, the first crystallographic orientation of the embedded microcrystallite 16 is (110).

Referring again to FIG. 2, in one aspect of the invention, the film 14 is excimer laser crystallized (E) using light 18 having a wavelength of about 308 nanometers (nm) or less.
LC) process. Further, the microcrystalline film 14
Is annealed at a temperature near the melting point of the amorphous material 15 for about 50 nanoseconds (ns). When the microcrystalline film 14 is silicon, the microcrystalline film 14 is annealed using an excimer laser at a temperature generally in the range of 900 ° C. to 1600 ° C. If the microcrystalline film 14 is silicon-germanium, the microcrystalline film 14 is typically annealed at a temperature in the range above 800C.

Alternatively, the microcrystalline film 14 is annealed in a heating furnace annealing process (not shown) at a temperature lower than about 600 ° C., usually for 3 hours to 3 days. In another aspect of the invention, microcrystalline film 14 is subjected to a rapid thermal anneal (RTA) crystallization process (not shown) to about 9%.
Anneal at a temperature below 00 ° C., usually for 1-5 seconds.

Referring again to FIG. 1, in one aspect of the invention, microcrystalline film 14 has a thickness of less than about 1000 °
Having. Referring again to FIG. 4, the polycrystalline film 31 having this thickness is suitable for manufacturing a thin film transistor. Preferably, microcrystalline film 14 has a thickness of less than about 500 °. The polycrystalline film 31 is very suitable for manufacturing this thin-film transistor. In the laser annealing process, the smaller the film thickness is, the larger the crystal grain tends to be. These larger particles are 2
It is observed in films having a thickness in the range of 0 to 50 nanometers (nm).

In one aspect of the present invention, the microcrystalline film 14
Is a plasma CV using a mixed gas of SiH ₄ and H _2.
Deposited by D (PECVD) process. The microcrystalline film 14 has a power level of about 600 watts, a temperature of about 320 ° C., a total pressure of about 1.2 Torr, 20 sccm SiH _4.
It is deposited under conditions of a flow rate and a H ₂ flow rate of 2000 sccm.

Alternatively, the microcrystalline film 14 is formed by low pressure CVD.
(LPCVD), ultra-high vacuum CVD, light CVD, high density plasma CVD, hot wire CVD, and deposited by a process selected from the group consisting of sputtering.

The microcrystalline film 14 is made of disilane (Si ₂ H ₆ ),
Formula Si _N H _{2N + 2} (where, N> 2) higher silane than is represented by, and the structural formula _{Si N H 2N + 2 / Si} N F
Deposited by a chemistry selected from the group consisting of a silane / fluorosilane chemical (where N ≧ 1) mixture represented by _{2N + 2} .

In one aspect of the present invention, microcrystalline film 14
Is deposited in an ultra-high vacuum environment, thereby minimizing contaminants.
Miniaturization improves the formation of microcrystallites 16.
When contaminants are present, the substrate between the silicon species and the impurities
Competition occurs for adsorption to surfaces. As a result,
The surface mobility of the deposited silicon species decreases and crystal lump forms.
Is more likely than in an environment free of gaseous impurities.
Smaller. Further, the transparent substrate 12 has a microcrystalline film 14 formed thereon.
Before being deposited, it is cleaned, so that
Of microcrystallite 16 is promoted. Washing
Pure is Ar, O _Two, N_TwoOr H_TwoOn-the-spot
Wet cleaning by rasma cleaning or elsewhere
Leaning chemical or mechanical means (ie bead brass
Ting).

FIG. 7 is a flowchart illustrating steps of a method for forming a polycrystalline film from a microcrystalline film. Step 50 provides a microcrystalline film for forming a polycrystalline film. Alternatively, step 50 provides a substantially amorphous film for forming a polycrystalline thin film transistor on a transparent substrate. Step 52 deposits a microcrystalline film including microcrystallite embedded in an amorphous material. Step 54 is a step 52
Annealing the deposited film in forming an at least partially polycrystalline film. Step 56 is the product,
The polycrystalline film is formed by including a seed crystal embedded in an amorphous material to promote formation of uniform crystal grains having a relatively large size. This process is also described in FIGS.

In one aspect of the invention, step 52
The microcrystalline film deposited at has two thicknesses, a first predetermined thickness, and a second predetermined thickness that covers the first thickness. Step 54 comprises melting the second thickness of the film, such that a controlled number of seed crystals within the thickness of the first film cause the formation of crystal grains having a substantially uniform size. Facilitate. This process is also illustrated in FIG.

In another aspect of the invention, step 54
Comprises selectively melting the amorphous material and heating the microcrystalline film deposited in step 52 such that a predetermined number of microcrystallites remain in the amorphous material without being melted. In this manner, a controlled number of seed crystals facilitates the formation of uniform, large-sized crystal grains.

The preferred embodiment of the present invention comprises a step 52
, Further comprising depositing a second completely amorphous film over the microcrystalline film deposited in step 52. Annealing in step 54 includes enlarging the crystalline region from the microcrystalline film to the second film. The film deposition process is accelerated with a completely amorphous film. The microcrystalline film has a predetermined first thickness, the second film has a predetermined second thickness, and the second thickness generally includes the first film and the second film. Less than about 25% of the combined thickness. FIG. 5 shows this process.

In one aspect of the invention, step 52
Involves embedding microcrystallites in an amorphous material, typically at a density of less than 10 ⁻⁸ cm ⁻² .
The distribution and size of the crystal grains are adjusted according to the number of seed crystals and the microcrystalline film. Step 52 also includes depositing a film comprising an amorphous material embedded with microcrystallites having a size typically in the range of 50 ° to 500 °. Control of the size and stability of the crystal mass is performed according to the size of the seed crystal.

In a preferred embodiment, step 5
The amorphous material and microcrystallite in the form deposited in 2 are silicon. Alternatively, the amorphous material and microcrystallite of the film deposited in step 52 are silicon-germanium compounds.

In one aspect of the invention, step 52
Comprises depositing a film in which microcrystallites embedded in an amorphous material have a uniform distribution pattern. Therefore, the number of grain boundaries is minimized.

In a preferred embodiment of the present invention, step 52 includes depositing a microcrystalline film embedded with microcrystallites having a substantially predetermined first crystallographic orientation. Step 54 includes annealing the polycrystalline film to have the first crystallographic microcrystallite deposited in Step 52.
By using the same crystal orientation throughout the polycrystalline film, grain boundaries are minimized. Preferably, the first crystallographic orientation of the embedded microcrystallite is (110)
It is.

In another preferred embodiment, step 5
(4) heating the microcrystalline film deposited in step 52 so as to selectively eliminate microcrystallites having no predetermined first crystal orientation; Annealing the microcrystalline film to have a first crystallographic orientation. By using the same crystal orientation throughout the polycrystalline film, grain boundaries are minimized. Preferably, the first crystallographic orientation of the embedded microcrystallite is (110).

In one aspect of the invention, step 54
Excimer laser crystallization (E) where the film deposited in step 52 is heated with light having a wavelength of about 308 nm or less.
LC) process. Further, step 54 includes annealing the microcrystalline film deposited in step 52 at a temperature near the melting point of the amorphous material for about 50 nanoseconds. If the microcrystalline film deposited in step 52 is silicon, step 54
Involves annealing the microcrystalline film at a temperature typically in the range of 900C to 1600C. If the microcrystalline film deposited in step 52 is silicon-germanium,
Step 54 involves annealing the microcrystalline film at a temperature typically in the range above 800 ° C.

Alternatively, step 54 comprises step 52
Annealing the microcrystalline film deposited in step 2 in a furnace anneal process in which the film is heated at a temperature less than about 600 ° C. for a time period typically in the range of 3 hours to 3 days. In another different aspect of the invention, step 54
Means that the microcrystalline film deposited in step 52 is
Annealing in a rapid thermal anneal (RTA) crystallization process, heating at a temperature below about 900 ° C. for a range of seconds.

In one aspect of the invention, step 52
Has the step of depositing a microcrystalline film having a thickness of less than about 1000 °, whereby the polycrystalline film is suitable for the manufacture of thin film transistors. Preferably, step 52 comprises depositing a microcrystalline film having a thickness of less than about 500 °, so that the polycrystalline film is well suited for thin film transistor fabrication.

In one aspect of the invention, step 52
Includes depositing a microcrystalline film by a PECVD process using a mixed gas of SiH ₄ and H ₂ . The microcrystalline film has a power level of about 600 watts, a temperature of about 320 ° C., a total pressure of about 1.2 Torr, 20 sccm SiH
Step 5 with ₄ flow rates and 2000 seem H ₂ flow rate
2 is deposited.

Alternatively, in step 52, the microcrystalline film is deposited by a process selected from the group consisting of LPCVD, ultra-high vacuum CVD, light CVD, high density plasma CVD, hot wire CVD, and sputtering.

In one aspect of the invention, the microcrystalline film is treated in step 52 with disilane (Si ₂ H ₆ )
i _N H _2N + 2 higher order silane from represented by (N> 2), and the structural formula _{Si N H 2N + 2 / Si} N F 2N + 2 (N ≧ 1)
Deposited by a chemistry selected from the group consisting of a silane / fluorosilane chemical mixture represented by

In one aspect of the invention, step 52
Comprises depositing a microcrystalline film in an ultra-high vacuum,
Thereby, minimizing contaminants enhances the formation of microcrystallites. In a preferred embodiment of the present invention,
A polycrystalline film is formed so as to cover the transparent substrate.
Step 2 includes depositing a microcrystalline film on a transparent substrate.
The transparent substrate is selected from the group consisting of quartz, glass, and plastic. The polycrystalline film is suitable for manufacturing a thin film transistor for a liquid crystal display. Further, step 52 includes cleaning the transparent substrate prior to depositing the microcrystalline film, thereby facilitating the formation of microcrystalline in the microcrystalline film.

A specific example of a method for forming a polycrystalline film will be described below. Also compare the polycrystalline film of the present invention with results obtained from a conventional amorphous silicon process. Suitable deposition conditions are shown in Table 1 below. Both film forming processes were performed under the same conditions below. 1) 30 sample sizes 2) Use of excimer laser in ambient air 3) Substrate temperature 400 ° C 4) 95% laser beam overlap 5) 65 mm x 2 mm beam size 6) Rated energy density 300 mJ / cm ²

[0118]

[Table 1]

After laser annealing, both groups of samples were examined by Raman spectroscopy. As is well known in the art, Raman spectroscopy is a technique that provides information on binding in a sample, which in turn provides qualitative and quantitative information about the crystal structure. Important responses to Raman spectroscopy are peak position and peak full width at half maximum (FWHM).

Table 2 shows the average of the Raman characteristics of 30 samples (per material group) analyzed by Raman spectroscopy. Regarding the phase of the starting material, the amorphous silicon film as deposited is called amorphous silicon, and the microcrystalline silicon film as deposited is called μc-Si. As shown in Table 2, the average peak shift and peak FWHM are significantly different between the two groups of materials, with the peak shift increasing when the as-formed film is deposited in the microcrystalline phase. , FWHM decreases. These observations are consistent with a higher degree of crystallinity (ie, lower defect density), and a larger grain size for the as-deposited microcrystalline silicon film.

[0121]

[Table 2]

Table 2 shows the average peak shift and peak F
Shows that WHM is significantly different between the two groups. When a microcrystalline membrane (μ crystallite) membrane is used, the peak shift increases and the peak FWHM decreases. These observations are consistent with a polycrystalline film having a higher degree of crystallinity and a larger grain size.

A transmission electron microscope (TEM) was used to measure the particle size. Particle size measurements were performed using digitized TEM micrographs using an image processing software package. Usually 200 to 300
Individual particles were measured for each sample. Using this approach, the equivalent particle size is calculated by:

[0124]

(Equation 1)

In the formula (1), r is the equivalent particle size, a is the main axis of the particle, and b is the short axis of the particle.

FIG. 8 shows the correlation between the average particle sizes of the amorphous film and the microcrystalline film of the present invention. Particle is TE
M and the FWHM of the crystal peak was measured by Raman spectroscopy. Based on the general trend of the data shown in FIG. 8, it can be concluded that the FWHM of the crystalline peak decreases as the average grain size of the polycrystalline film increases.
In a previous study, it was reported that a sharper crystal peak was observed for a film having higher crystallinity. The structural quality of a polycrystalline film depends on at least two major components: (a) the grain size, which determines the density of grain boundaries, ie, determines the density of grain boundary defects; Having. For laser-annealed polysilicon films, typically low intragranular defect densities are obtained, and thus changes in FWHM are primarily related to changes in the grain size of the polysilicon material.

The value of FWHM shown in FIG. 8 is an average value obtained by performing five measurements for each sample. Some variation is expected, as indicated by the associated error bars. The standard deviation of the FWHM values decreased with particle size and was found to be on the order of 0.15 for samples with smaller particle sizes. Using a linear model shown by a straight line in FIG.
Results in uncertain results at a particle size of about 30 nm. Therefore, differences in average particle size below 25 nm cannot be detected with this model (unless further FWHM measurements are obtained for each sample). Instabilities in FWHM measurements are mainly caused by the dispersive nature of the particle size and certain variations over the length of the laser beam in the ELA process. Usually an area of 30 μm ² is used for sampling while obtaining the spectrum of the film. Within this region, there may be different particle “mixtures” depending on the location of the region along the length of the beam. Larger particles (on average) are sampled when the control region is closer to the center of the laser beam than closer to the edge of the laser beam. Thus, the degree of homogeneity over the length of the beam reflects the uniformity of the Raman characteristics for a given sample.
As can be seen from the data in FIG. 8, the standard deviation of the FWHM measurements decreases as the particle size decreases. This is in excellent agreement with the experimentally observed reduction in the standard deviation of particle size in polysilicon films having smaller particle sizes (Table 2).

FIG. 9 shows the difference between the average values of the amorphous film of the present invention and the microcrystalline film. A one-to-one comparison was made on the particle size distribution between polysilicon films formed by ELA of a-Si or μc-Si films. This is a comparison aimed at identifying significant statistical differences between the two populations. For this purpose, samples annealed with an actual energy density of 300 mJ / cm ² (same as the set point) were selected and compared.

The results in FIG. 9 support the successful importance at the 1% level. That is, the two populations have significantly different average values. Further, as shown in FIG.
The polysilicon film formed by the i-ELA shows an average particle size almost twice as large.

The present invention offers exciting possibilities for a new generation of high performance TFTs. Polycrystalline films formed according to the present invention have larger crystal grains (1 μm or more) and relatively uniform size crystal grains (less than 5% uniformity).
Having. Because the particles are large and uniform, transistors have good switching properties, good electron mobility, and consistent behavior across the film. By improving the switching characteristics of a transistor formed from a polycrystalline film, a driver circuit which has conventionally been arranged on the periphery of a transparent substrate can be arranged directly on the substrate. In this manner, the size and complexity of the LCD is reduced. Other embodiments of the invention will be apparent to those skilled in the art.

[0131]

According to the present invention, there is provided a method for forming a thin film transistor semiconductor film made of polycrystalline silicon on a transparent substrate, which is suitable for manufacturing a liquid crystal display. A film consisting essentially of amorphous silicon is deposited on the transparent substrate. Small silicon seed crystals are contained in the amorphous silicon. When amorphous silicon is annealed, the seed crystal becomes crystal grains,
Eventually, it will be polycrystalline silicon. The seed crystal helps to adjust the annealing process and reduces the process dependence on accurate placement and heating methods. The use of seed crystals also ensures that the size of the crystal grains is large and uniform. Large particles facilitate the production of TFTs that have high mobility and exhibit uniform performance across the LCD. Also provided is an LCD having a layer of TFT polycrystalline film on a transparent electrode formed by annealing substantially amorphous silicon including a seed crystal.

[Brief description of the drawings]

FIG. 1 illustrates steps in a method of forming an LCD.

FIG. 2 illustrates steps in a method for forming an LCD.

FIG. 3 illustrates steps in a method of forming an LCD.

FIG. 4 illustrates steps in a method of forming an LCD.

FIG. 5 shows that the deposited microcrystalline film has two thicknesses
3 is a partial cross-sectional view of the LCD of FIG.

6 is a partial cross-sectional view of the LCD of FIG. 1 further including a second completely amorphous film overlying the microcrystalline film.

FIG. 7 is a flowchart illustrating steps in a method for forming a polycrystalline film from a microcrystalline film.

FIG. 8 is a diagram showing a correlation between the average particle size of the amorphous film and the average particle size of the microcrystalline film of the present invention.

FIG. 9 is a table showing a difference between average values of an amorphous film and a microcrystalline film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 LCD 12 Transparent substrate 14 Microcrystal film 15 Amorphous substance 16 Seed crystal 17 Thickness 18 Laser beam 24 Microcrystal 26 Region 28, 30 Crystal particle 31 TFT polycrystalline semiconductor film 32, 38 First thickness 34, 40 Second Thickness 36 Amorphous film

Claims (60)

[Claims] 1. A method of forming a polycrystalline film from a microcrystalline film, the method comprising: a) depositing a microcrystalline film including microcrystallite embedded in an amorphous material; b) the step annealing the film deposited in a) to form an at least partially polycrystalline film, whereby a uniform size having a relatively large size is obtained by including an embedded seed crystal in the amorphous material. Promoting the formation of fine crystalline particles. 2. The microcrystalline film deposited in step a) has two thicknesses, a first predetermined thickness and a second predetermined thickness covering the first thickness. , Said step b) comprises melting said second thickness of the film, whereby a controlled number of seed crystals within the thickness of said first film are uniform and large in size. 2. The method of claim 1, which promotes formation. 3. The method according to claim 1, wherein the step (b) comprises heating the microcrystalline film deposited in the step (a) so as to selectively melt the amorphous material. The method of claim 1, wherein the light remains unmelted, whereby a controlled number of seed crystals promotes the formation of uniform, large-sized crystal grains. 4. The method according to claim 1, further comprising, following said step a), depositing a second film of a completely amorphous material covering said microcrystalline film deposited in said step a). The method of claim 1, wherein the annealing comprises expanding a crystalline region from the microcrystalline film into a second film, whereby the film deposition process is faster with the use of a completely amorphous film. 5. The microcrystalline film has a predetermined first thickness, the second film has a predetermined second thickness, and the second thickness is generally equal to the first thickness. The method of claim 4, wherein the combined thickness is less than about 25% of the thickness of the first and second thicknesses. 6. The method according to claim 1, wherein said step a) comprises placing said microcrystalline in said amorphous material, typically at 10 ⁻⁸ cm ^−2.
The method of claim 1, comprising embedding at a density of less than, whereby the distribution and size of the crystal grains is adjusted according to the number of seed crystals in the microcrystalline film. 7. The method according to claim 1, wherein said step a) is performed in a range of 50 to 50 degrees.
Claims: comprising depositing a film comprising an amorphous material embedded with microcrystallites having a size in the range of 0 °, whereby control over crystallite size and stability is responsive to the size of the seed crystal. 2. The method according to 1. 8. The method of claim 1, wherein the amorphous material and the microcrystallite of the film deposited in step a) are silicon. 9. The method of claim 1, wherein the amorphous material and the microcrystallite of the film deposited in step a) are silicon-germanium compounds.
The method described in. 10. The step a) of depositing a film in which the microcrystallites embedded in the amorphous material have a uniform distribution pattern, whereby the number of grain boundaries is minimized. Claim 1.
The method described in. 11. The step (a) includes depositing a microcrystalline film having microcrystallite embedded therein having a substantially predetermined first crystallographic orientation, and the step (b) includes the step (a). The first deposited at
Annealing the polycrystalline film to have microcrystallites of the following crystal orientation, whereby grain boundaries are minimized by using the same crystal orientation throughout the polycrystalline film. The described method. 12. The method of claim 11, wherein the first crystallographic orientation of the embedded microcrystallite is (110). 13. The step b) of heating the microcrystalline film deposited in the step a) so as to selectively eliminate microcrystallites having no predetermined first crystallographic orientation; Annealing the microcrystalline film to have substantially the remaining microcrystalline of the first crystallographic orientation, such that the same crystallographic orientation throughout the polycrystalline film is at a grain boundary. 2. The method of claim 1, wherein is minimized. 14. The embedded microcrystallite having a first crystal orientation of (110).
The method described in. 15. The method of claim 1, wherein step b) includes annealing the film deposited in step a) with an excimer laser crystallization (ELC) process that heats the film with light having a wavelength of about 308 nm or less. 2. The method according to 1. 16. The method according to claim 1, wherein the step b) is performed in the step a).
The method of claim 15, comprising annealing the microcrystalline film deposited at a temperature near the melting point of the amorphous material for about 50 nanoseconds. 17. The method according to claim 17, wherein the microcrystalline film deposited in step a) is silicon,
17. The method of claim 16, comprising annealing the microcrystalline film at a temperature in the range of 0C to 1600C. 18. The microcrystalline film deposited in step a) is silicon-germanium, and step b) includes annealing the microcrystalline film at a temperature typically above 800 ° C. The method described in. 19. The step b) comprises annealing the microcrystalline film deposited in the step a) in a furnace annealing process in which the microcrystalline film is heated at a temperature of less than about 600 ° C. for a period usually ranging from 3 hours to 3 days. The method of claim 1, comprising a step. 20. The rapid thermal anneal (RTA) crystallization in which step b) comprises heating the microcrystalline film deposited in step a) at a temperature below about 900 ° C., typically for 1-5 seconds. The method of claim 1, comprising annealing in the process. 21. Step a) includes depositing a microcrystalline film having a thickness of less than about 1000 °;
The method according to claim 1, wherein the polycrystalline film is suitable for manufacturing a thin film transistor. 22. The method of claim 1, wherein said step a) comprises depositing a microcrystalline film having a thickness of less than about 500 °, whereby said polycrystalline film is well suited for thin film transistor fabrication. the method of. 23. The method of claim 1, wherein step a) includes depositing the microcrystalline film by a PECVD process using a gas mixture of SiH ₄ and H ₂ . 24. The method according to claim 24, wherein the microcrystalline film comprises a power level of about 600 W, a temperature of about 320 ° C.
Total pressure of about 1.2 Torr, is deposited under the condition that the flow rate _of SiH ₄ and 2000sccm the flow rate of H ₂ of 20 sccm, The method of claim 23. 25. The method according to claim 25, wherein the microcrystalline film is formed in step a) under reduced pressure CVD (LPCVD), ultrahigh vacuum CVD, photo CVD, high density plasma CVD, hot wire CVD,
2. The method of claim 1, wherein the method is deposited by a process selected from the group consisting of: and sputtering. 26. The microcrystalline film according to claim 1, wherein in step a), disilane (Si ₂ H ₆ ), formula Si _N H _{2 N + 2} (N>
Higher silane than is represented by 2), and the structural formula _{Si N H 2N + 2 / Si} N F 2N + 2 (N ≧ 1) the group consisting of a chemical mixture of silane / fluoro silane represented by 4. The method of claim 1, wherein the deposition is by a selected chemistry.
The method described in. 27. The method of claim 27, wherein step a) includes depositing the microcrystalline film in an ultra-high vacuum, thereby improving microcrystallite formation by minimizing contaminants. 2. The method according to 1. 28. The polycrystalline film is formed to cover a transparent substrate, and the step a) includes depositing the microcrystalline film on the transparent substrate, whereby the polycrystalline film is formed of a liquid crystal. The method according to claim 1, which is suitable for manufacturing a thin film transistor for a display (LCD). 29. The method according to claim 29, wherein the step a) includes cleaning the transparent substrate before depositing the microcrystalline film.
29. The method according to claim 28, whereby the formation of microcrystallites in said microcrystalline film is promoted. 30. The transparent substrate is selected from the group consisting of quartz, glass, and plastic.
The method described in. 31. A method for forming a thin film transistor comprising a polycrystalline film from a substantially amorphous film on a transparent substrate, the method comprising the steps of: a) usually having a density of less than 10 ⁻⁸ cm ^−2. Embedding microcrystallites in an amorphous silicon material, said microcrystallites typically being between 50 ° and 50 °
Forming a microcrystalline material having a size of 0 °, and b) subjecting the microcrystalline material of step a) to a PECVD process using a mixed gas of SiH ₄ and H ₂ for about 60
0 W power level, about 320 ° C. temperature, about 1.2 Torr
r total pressure, 20 sccm SiH ₄ flow rate and 2000
depositing on said transparent substrate under conditions of H ₂ flow rate of sccm; c) forming a film from said microcrystalline material deposited in said step b) to a total thickness of less than about 500 ° D) heating the film deposited in step a) with light having a wavelength of less than about 308 nm in an ELC process; e) increasing the thickness of the second film to a temperature typically between 900 ° C and 1600 ° C. Melts at a range of temperatures for 50 nanoseconds to form at least partially a polycrystalline film, thereby promoting the formation of uniform crystalline particles having a relatively large size by including seed crystals in the amorphous material. Performed. 32. A liquid crystal display (LCD) comprising a transparent substrate and a TFT polycrystalline semiconductor film, wherein the semiconductor film covers the transparent substrate and has an amorphous microcrystallite embedded therein. A microcrystalline film comprising a material is formed by depositing on the substrate and annealing the microcrystalline film, thereby having a relatively large size by including a seed crystal embedded within the amorphous material A semiconductor film in which formation of uniform crystal grains is promoted. 33. The microcrystalline film, wherein the deposited microcrystalline film includes two thicknesses, a predetermined first thickness, and a predetermined second thickness covering the first thickness. Annealing comprises melting the thickness of the second film so that a controlled number of the seed crystals within the thickness of the first film are uniform and large in size. 33. The LCD of claim 32, which facilitates formation. 34. The microcrystalline film is heated to selectively melt the amorphous material, and a predetermined number of the microcrystallites remain unmelted in the amorphous material, thereby being controlled. 33. The LCD of claim 32, wherein a number of said seed crystals promote the formation of uniform, large size crystal grains. 35. The method of claim 25, further comprising a second film of completely amorphous material overlying the microcrystalline film, wherein the annealing expands a crystalline region from the microcrystalline film into the second film, 33. The LC of claim 32, wherein the use of the completely amorphous film speeds up the film deposition process.
D. 36. The microcrystalline film has a predetermined first thickness, the second film has a predetermined second thickness, and the second thickness is generally the first thickness. 36. The LC of claim 35, wherein the thickness is less than about 25% of the combined thickness of the first and second thicknesses.
D. 37. The density of the microcrystallite embedded in the microcrystalline film is typically less than 10 ⁻⁸ cm ⁻² , such that the distribution and size of crystal grains is reduced by the seeds in the microcrystalline film. 33. The LCD according to claim 32, wherein the LCD is adjusted according to the number of crystals. 38. The microcrystalline film is usually formed at a temperature of 50 °
33. The LCD of claim 32, wherein the microcrystallite having a size in the range of Å is embedded, so that control over crystallite size and stability is responsive to the size of the seed crystal. 39. The amorphous material and the microcrystallite of the microcrystalline film are silicon,
An LCD according to claim 32. 40. The LCD according to claim 32, wherein the amorphous material and the microcrystallite of the microcrystalline film are a silicon-germanium compound. 41. The LCD of claim 32, wherein the microcrystallites embedded in the amorphous material have a uniform distribution pattern, thereby minimizing the number of grain boundaries. 42. The microcrystallite embedded in the microcrystalline film has a substantially predetermined first crystal orientation, and the polycrystalline film has a microcrystallite of the first crystal orientation. 33. The LCD of claim 32, wherein grain boundaries are minimized by using the same crystallographic orientation throughout the polycrystalline film. 43. The LCD of claim 42, wherein the first crystallographic orientation of the embedded microcrystallite is (110). 44. The microcrystalline film is selectively heated so as to eliminate microcrystallites having no predetermined first crystal orientation, and substantially remaining microcrystallites are removed from the first crystallite. 4. The microcrystalline film is annealed to have an orientation, whereby the same crystallographic orientation throughout the polycrystalline film minimizes grain boundaries.
2. The LCD according to 2. 45. The LCD of claim 44, wherein the first crystallographic orientation of the embedded microcrystallite is (110). 46. An excimer laser crystallization (EL) method wherein the microcrystalline film uses light having a wavelength of about 308 nm or less.
33. L according to claim 32, which is annealed in a C) process.
CD. 47. The microcrystalline film is annealed at a temperature near the melting point of the amorphous material for about 50 nanoseconds.
The LCD according to claim 46. 48. The LCD of claim 47, wherein said microcrystalline film is silicon and said microcrystalline film is annealed at a temperature typically in the range of 900 ° C. to 1600 ° C. 49. The LCD of claim 47, wherein the microcrystalline film is silicon-germanium and the microcrystalline film is annealed at a temperature typically greater than 800 ° C. 50. The LC of claim 32, wherein the microcrystalline film is annealed in a furnace anneal process at a temperature less than about 600 ° C. for a period typically ranging from 3 hours to 3 days.
D. 51. The method according to claim 51, wherein the microcrystalline film is formed at a temperature of less than about 900 ° C. for a period of time ranging from 1 to 5 seconds.
Annealed in an annealing (RTA) crystallization process,
An LCD according to claim 32. 52. The LCD of claim 32, wherein the microcrystalline film has a thickness of less than about 1000 °, whereby the polycrystalline film is suitable for manufacturing a thin film transistor. 53. The LCD of claim 32, wherein said microcrystalline film has a thickness of less than about 500 °, whereby said polycrystalline film is well suited for thin film transistor fabrication. 54. The LCD according to claim 32, wherein the microcrystalline film is deposited by a PECVD process using a mixed gas of SiH ₄ and H ₂ . 55. The microcrystalline film is provided with a power level of about 600 W, a temperature of about 320 ° C., a total pressure of about 1.2 Torr,
0 sccm SiH ₄ flow rate and 2000 sccm H ₂
55. The L according to claim 54, wherein the L is deposited under flow conditions.
CD. 56. The microcrystalline film is formed by low pressure CVD (LPC).
VD), ultra-high vacuum CVD, optical CVD, high-density plasma C
33. The LCD of claim 32, wherein the LCD is deposited by a process selected from the group consisting of VD, hot wire CVD, and sputtering. 57. The microcrystalline film is made of disilane (Si
₂ H ₆ ), higher order silanes represented by the formula Si _N H _{2N + 2} (N> 2), and the structural formula Si _N H _{2N + 2} / Si _N F
_33. The LCD of claim 32, wherein the LCD is deposited by a chemistry selected from the group consisting of a silane / fluorosilane chemical mixture represented by _{2N + 2} (N> 1). 58. The LCD of claim 32, wherein the microcrystalline film is deposited in an ultra-high vacuum environment, thereby enhancing the formation of the microcrystallite by minimizing contaminants. 59. The transparent substrate is cleaned before the microcrystalline film is deposited, thereby promoting the formation of the microcrystallite in the microcrystalline film.
2. The LCD according to 2. 60. The transparent substrate is selected from the group consisting of quartz, glass, and plastic.
LCD described in 1.