CN102099895B - Method for producing crystalline film and apparatus for producing crystalline film - Google Patents

Abstract

The present invention provides a method and an apparatus for manufacturing a crystalline film, wherein an amorphous film is irradiated with radiation having a wavelength of 340 to 358nm and a wavelength of 130 to 240mJ/cm for 1 to 10 times²The pulse laser of energy density of (1) is preferably a pulse laser having a pulse width of 5 to 100ns, a frequency of 6 to 10kHz, and a minor axis width of 1.0mm or less, and the pulse laser is relatively scanned at a scanning speed of 50 to 1000 mm/sec, so that a uniform and fine crystal film having small variations in crystal grain diameter can be efficiently formed from the amorphous film without damaging the substrate.

Description

Method for producing crystalline film and apparatus for producing crystalline film

technical field

The present invention relates to a method and apparatus for producing a crystalline film by irradiating an amorphous film with pulsed laser light to finely crystallize the amorphous film to form a crystalline film.

Background technique

In order to manufacture crystalline silicon for thin-film transistors (TFTs) used in flat-panel displays such as liquid crystal displays, the following two methods are generally used. One method is the laser annealing method in which pulses are irradiated to the amorphous silicon film provided on the upper layer of the substrate. Laser to make it melt and recrystallize; another method is solid phase growth (SPC, Solid Phase Crystallization), using a heating furnace to heat the substrate with an amorphous silicon film on the upper layer, without making the silicon film Melts to grow crystals in a solid state.

Also, the present inventors confirmed that a polycrystalline film finer than solid-phase growth can be obtained by irradiating pulsed laser light while maintaining the substrate temperature in a heated state, and filed a patent application (see Patent Document 1).

Patent Document 1: Japanese Patent Laid-Open No. 2008-147487

Contents of the invention

In recent years, in the manufacture of OLED (Organic light-emitting diode) panels or LCD (Liquid Crystal Display) panels for large TVs, it is desired to produce uniform and large-area fine polysilicon films at low cost. Methods.

In addition, recently, in an organic EL display replacing a liquid crystal display as the most promising next-generation display, the luminance of the screen is increased by the organic EL itself emitting light. Since the light-emitting material of organic EL is not driven by voltage like LCD, but by current, the requirements for TFT are different. In a TFT made of amorphous silicon, it is difficult to suppress aging, and the threshold voltage (Vth) will drift greatly, which limits the lifetime of the device. Polysilicon, on the other hand, has a longer lifetime because it is a stable material. However, in TFTs made of polysilicon, the characteristics of TFTs vary widely. This variation in TFT characteristics is more likely to occur due to variation in crystal grain diameter and the presence of interfaces (grain boundaries) of crystal grains of crystalline silicon in the TFT channel formation region. Variation in characteristics of TFTs is easily influenced mainly by the diameter of crystal grains and the number of grain boundaries existing between channels. In addition, when the crystal grain diameter is large, electron mobility generally becomes large. TFTs for organic EL displays have high electric field electron mobility, but the channel length of the TFT must be extended. The size of one pixel for each of RGB (red, green, blue) depends on the channel length of the TFT, and high resolution cannot be obtained. Therefore, there is an increasing demand for a fine crystal film with less variation in crystal grain diameter.

However, in the existing crystallization method, it is difficult to solve these problems.

This is because one of the laser annealing methods is a process of temporarily melting and recrystallizing amorphous silicon. Generally, the diameter of the formed crystal grains is large, and the deviation of the crystal grain diameter is also large. Therefore, as explained above, the electric field electron mobility is high, and the number of crystal grain diameters in the channel region of a plurality of TFTs varies, as well as the random shape and the difference in the crystal orientation of adjacent crystals. Greatly affects the characteristic variation of TFT. In particular, differences in crystallinity tend to occur in laser superimposed portions, and this difference in crystallinity greatly affects variations in TFT characteristics. In addition, there is also a problem that crystal defects are generated due to contamination (impurities) on the surface.

In addition, the crystals obtained by the solid phase growth method (SPC method) have a small particle size and a small TFT deviation, which is the most effective crystallization method to solve the above-mentioned problems. However, its crystallization time is long, and it is difficult to use it for mass production. In the heat treatment process capable of solid phase growth (SPC), a batch type heat treatment apparatus that processes a plurality of substrates at the same time is used. Since a large number of substrates are heated at the same time, it takes a long time to heat up and cool down, and the temperature inside the substrates tends to be uneven. In addition, if the solid-phase growth method is heated at a temperature higher than the deformation point temperature of the glass substrate for a long time, the glass substrate itself will shrink and expand, and the glass will be damaged. Since the crystallization temperature of SPC is higher than the glass transition temperature, a small temperature distribution will cause bending or shrinkage distribution of the glass substrate. As a result, even if crystallization is possible, problems arise in processes such as the exposure process, making it difficult to manufacture devices. The higher the processing temperature, the greater the need for temperature uniformity. In general, the crystallization rate depends on the heating temperature, and requires 10 to 15 hours at 600°C, 2 to 3 hours at 650°C, and tens of minutes at 700°C. In order to process without damaging the glass substrate, a long process time is required, and this method is difficult to use for mass production.

The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a method for producing a crystalline film capable of efficiently producing a fine crystalline film with less variation in crystal grain diameter from an amorphous film without damaging a substrate.

That is, in the method for producing a crystalline film of the present invention, the first aspect of the present invention is characterized in that the amorphous film existing on the upper layer of the substrate is irradiated with a crystalline film formed at a wavelength of 340 to 358 nm with the number of irradiations of 1 to 10 times. , a pulsed laser with an energy density of 130-240 mJ/cm ² , heating the amorphous film to a temperature not exceeding the crystal melting point to crystallize it.

The crystalline film manufacturing device of the present invention comprises: a pulsed laser light source, the pulsed laser light source outputs a pulsed laser with a wavelength of 340-358 nm; an optical system, which guides the pulsed laser to the amorphous film to irradiate it; an attenuator , the attenuator adjusts the attenuation rate of the pulse laser output from the pulse laser light source, so that the laser is irradiated on the amorphous film with an energy density of 130-240mJ/cm ² ; and a scanning device, the scanning The device moves the laser light relative to the amorphous film, and irradiates the pulsed laser light overlappingly within the range of 1 to 10 irradiations on the amorphous film.

According to the present invention, the amorphous film is heated to a temperature not exceeding the crystal melting point by irradiating the amorphous film with a pulsed laser in the ultraviolet wavelength region with a moderate energy density and a moderate number of irradiation times. The method of the melting and recrystallization method can obtain uniform fine crystals with small particle size deviation, for example, fine crystals with a size of 50 nm or less and no protrusions. In the conventional melt crystallization method, the crystal grain diameter is larger than 50nm, and in this melt crystallization method or SPC (solid phase growth method) using a heating furnace, the variation of crystal grains is large, and it is impossible to obtain Finely crystalline.

In addition, according to the present invention, since it is only heated to a temperature not exceeding the melting point of crystallization, the crystallized film itself does not undergo further phase change. The same crystallinity can be obtained, and the uniformity can be improved. In addition, by irradiating pulsed laser light according to the conditions of the present invention, the amorphous film can be heated to a temperature higher than that of the conventional solid phase growth method.

In addition, by using pulsed laser light instead of continuous oscillation, it is not easy to reach a temperature at which the substrate of the base is damaged. In addition, in the present invention, it is not necessary to heat the substrate, but as the present invention, heating the substrate is not excluded. However, in the present invention, it is preferable to perform the irradiation of the pulsed laser light without heating the substrate.

In addition, if the amorphous film provided on the substrate contains a lot of hydrogen, when it is irradiated with high energy such as the melt crystallization method, the molecular bond of Si-H may be easily broken and ablation may easily occur. However, in the present invention, since silicon remains in a solid state and is not easily ablated, it is possible to treat an amorphous film that has not been dehydrogenated.

Next, conditions specified in the present invention will be described.

Wavelength area: 340~358nm

Since the wavelength region is a wavelength region that absorbs better than amorphous films, especially amorphous silicon films, the pulsed laser light in this wavelength region can be used to directly heat the amorphous film. Therefore, it is not necessary to indirectly provide a laser light absorbing layer on an upper layer of the amorphous film. In addition, since the laser light is sufficiently absorbed by the amorphous film, the substrate can be prevented from being heated by the laser light, and the bending and deformation of the substrate can be suppressed, so that the substrate can be prevented from being damaged.

In addition, although the wavelength of laser light is absorbed by an amorphous film, especially an amorphous silicon film, if it is transmitted, the absorptivity of light in the irradiated part of the amorphous film is very low due to multiple reflections from the lower layer side. It largely depends on the variation in the thickness of the lower layer of the amorphous film. In this wavelength region, since laser light can be completely absorbed by an amorphous film, especially a silicon film, a polycrystalline film can be obtained without much consideration of variations in the film thickness of the underlying layer. In addition, since the transmission of the amorphous film is almost negligible, it can also be applied to a case where an amorphous film is formed on a metal.

That is, if the wavelength region of the laser light used for crystallization is set as the visible region, although silicon with a thickness of about 500 nm partly _absorbs light, there is also partly transmitted light. Influenced by multiple reflections of the buffer layer such as the SiN layer), the thickness of the buffer layer under the silicon is not uniform, and the light absorptivity of the silicon also changes. Even the method in which a cap layer such as SiO ₂ is provided on the upper layer of silicon has the same problem.

In addition, if the wavelength region of the pulsed laser light is in the infrared region, since silicon with a thickness of about 50 nm hardly absorbs light, a light-absorbing layer is generally provided on the upper layer of the silicon. However, if this method is used, the process of applying a light-absorbing layer and the process of removing the light-absorbing layer after pulsed laser irradiation will naturally be added.

From the above viewpoints, in the present invention, the wavelength region of the pulsed laser light is set to 340 to 358 nm in the ultraviolet region.

Energy density: 130～240mJ/cm ²

By irradiating the amorphous film with pulsed laser light with a moderate energy density (on the amorphous film), the amorphous film remains in the solid phase or is heated to a temperature exceeding the melting point of the amorphous material and not exceeding the melting point of the crystal to be crystallized. made into microcrystals. If the energy density is low, the temperature of the amorphous film cannot be raised sufficiently, and crystallization cannot be achieved sufficiently, and crystallization becomes difficult. On the other hand, if the energy density is high, molten crystallization will occur, resulting in ablation. Therefore, the energy density of the pulsed laser is limited to 130-240 mJ/cm ² .

Exposure times: 1 to 10 times

When irradiating an amorphous film with pulsed laser light, by appropriately setting the number of times of irradiation on the same area, even if there is an energy deviation in the irradiated beam area, the temperature of crystallization can be made uniform by multiple irradiations, and the final product into uniform crystallites.

If the number of times of irradiation is large, the amorphous film may be heated to a temperature exceeding the crystal melting point, thereby causing melting or ablation. In addition, as the number of irradiations increases, the processing time will become longer and the efficiency will be poor.

Crystallinity: 60-95%

Within the conditions of the wavelength, energy density, and number of irradiations mentioned above, the degree of crystallization during crystallization is preferably set at 60 to 95%. When the crystallinity is less than 60%, it is difficult to obtain sufficient characteristics when used as a thin film transistor or the like. If the energy applied to the amorphous film is small, the degree of crystallinity cannot be increased to 60% or more. In addition, if the degree of crystallinity exceeds 95%, the crystals gradually become coarser, making it difficult to obtain fine and uniform crystals. If the pulse laser is irradiated beyond the crystal melting point, the degree of crystallinity tends to exceed 95%.

In addition, specifically, the degree of crystallinity can be determined according to the ratio of the area of the crystalline peak and the area of the amorphous peak obtained by Raman spectroscopy (area of the crystallized Si peak/(area of the amorphous Si peak+the area of the crystallized Si peak area)) to decide.

In addition, the pulse width (half-amplitude width) of the pulse laser is preferably set to 5 to 100 ns. If the pulse width is small, the maximum power density increases, and it may be heated to a temperature exceeding the melting point, resulting in melting or ablation. In addition, if the pulse width is large, the maximum power density decreases, and it may not be possible to heat to a temperature at which the solid phase crystallizes.

In addition, the pulse frequency of the pulse laser is preferably 6 to 10 kHz.

By increasing the pulse frequency of the pulsed laser to a certain extent (above 6kHz), since the time interval between irradiations is shortened, the heat generated by the pulsed laser irradiation is retained by the amorphous film, so that crystallization can be effectively exerted. On the other hand, if the pulse frequency becomes too high, melting and ablation are likely to occur.

In addition, the short-axis width of the pulsed laser light is preferably 1.0 mm or less.

By relatively scanning the pulsed laser light in the short-axis width direction, the amorphous film can be partially irradiated and heated, and crystallization can be performed over a wide range. However, if the short-axis width is too large, it is necessary to increase the scanning speed for efficient crystallization, which increases the device cost.

By scanning the pulsed laser light against the amorphous film, the amorphous film can be crystallized in the surface direction. This scanning may move the pulsed laser side, the amorphous film side, or both. The scanning is preferably performed at a speed of 50-1000 mm/sec.

If the scanning speed is low, the maximum power density increases, and the amorphous film may be heated to a temperature exceeding the crystal melting point, thereby causing melting or ablation. In addition, when the scanning speed is high, the maximum power density decreases, and it may not be possible to heat to a temperature at which the solid phase is crystallized.

In addition, the production apparatus of the present invention can use a solid-state laser light source that outputs pulsed laser light in the ultraviolet region to output pulsed laser light in a desired wavelength range, so that microcrystals can be produced using a laser light source with good maintainability. In order to obtain uniform microcrystals, the energy density can be appropriately adjusted by an energy adjustment unit, and then the amorphous film can be irradiated with pulsed laser light. The energy adjustment unit may adjust the output of the solid-state laser light source to obtain a predetermined energy density, or may adjust the attenuation rate of the pulsed laser light output from the solid-state laser light source to adjust the energy density. By relatively scanning the pulsed laser light on the amorphous film with a scanning device, it is possible to obtain fine and uniform crystals with an appropriate degree of crystallization over a wide area of the amorphous film. The pulse frequency, the short-axis width of the pulsed laser light, and the scanning speed are set by this scanning so that the number of times of irradiation to the same region of the amorphous film is 1-10.

The scanning device may move the optical system that guides the pulsed laser light to move the pulsed laser light, or may move the susceptor on which the amorphous film is placed.

As explained above, according to the present invention, the amorphous film located on the upper layer of the substrate is irradiated with a pulsed laser light having a wavelength of 340-358 nm and an energy density of 130-240 mJ/cm ² with the number of irradiations of 1-10 times, The amorphous film is crystallized by heating to a temperature not exceeding the melting point of the crystal, and therefore, it is possible to fabricate a film having an average crystal grain size so small that a plurality of crystal grains exist in the channel region of the TFT, which has particularly excellent uniformity The crystalline film can solve the above problems. Recently, since the wiring width is becoming smaller, and the size (channel length, channel width) of the TFT channel formation region is also becoming smaller, there is a need for a method that can uniformly produce a small average particle size over the entire substrate area. method for stable crystalline films. There is a particular need for a crystallization technique that minimizes the difference in TFT characteristics of adjacent regions, which can be reliably achieved with the present invention. At the same time, it can also remove impurities attached to the surface of the membrane.

In addition, according to the present invention, the cost and maintenance cost of the apparatus can be reduced, and processing with a high operating rate can be performed, thereby improving productivity.

In addition, according to the present invention, since a process that can be processed at a low temperature regardless of whether the transition point of the substrate (glass substrate, etc.) or beyond the transition point is adopted, only the amorphous film can be heated by laser light. to high temperature to crystallize it. At the same time, it has the effect that a crystallite of 50 nm or less can be formed in a short time. At the same time, it has the effect that the same crystallites of 50 nm or less can be formed in the superimposed part (effective for large-area crystallization).

At the same time, it has the effect of suppressing the deformation (bending, deformation, internal stress) of the substrate to a minimum. At the same time, it has the effect of removing impurities present in the amorphous film and contaminants adhering to the surface by slightly heating the substrate.

Description of drawings

FIG. 1 is a longitudinal sectional view showing an ultraviolet solid-state laser annealing apparatus as a manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is an SEM photograph showing a thin film irradiated with a pulsed laser while changing the manufacturing conditions in the same example.

FIG. 3 is a SEM photograph showing a thin film irradiated with a pulsed laser light while changing the manufacturing conditions in other examples.

FIG. 4 is a SEM photograph showing a thin film irradiated with a pulsed laser while changing the manufacturing conditions in the same manner in other Examples.

FIG. 5 is a diagram similarly showing the measurement results of Raman spectroscopy.

detailed description

Next, one embodiment of the present invention will be described based on FIG. 1 .

In the manufacturing method of the crystalline film of the present embodiment, it is assumed that a substrate 8 used for a TFT device of a flat panel display is used as an object, and an amorphous silicon thin film 8 a is formed as an amorphous film on the substrate 8 . The amorphous silicon thin film 8a is formed on the upper layer of the substrate 8 by a usual method, and dehydrogenation treatment is omitted.

However, as the present invention, the type of the target substrate and the amorphous film formed thereon is not limited thereto.

1 is a diagram showing an ultraviolet solid-state laser annealing apparatus 1 used in a method for producing a crystal film according to an embodiment of the present invention, and the ultraviolet solid-state laser annealing apparatus 1 corresponds to the crystal film production apparatus of the present invention.

In the ultraviolet solid-state laser annealing treatment device 1, the ultraviolet solid-state laser oscillator 2 outputting a pulsed laser light with a wavelength of 340-358nm, a pulse frequency of 6-10kHz, and a pulse width of 5-100ns is arranged on the devibration table 6, and This ultraviolet solid-state laser oscillator 2 includes a control circuit 2a for generating a pulse signal.

An attenuator 3 is disposed on the output side of the ultraviolet solid-state laser oscillator 2 , and an optical fiber 5 is connected to the output side of the attenuator 3 via a coupler 4 . The transmission destination of the optical fiber 5 is connected to an optical system 7 including focusing lenses 70a, 70b, beam homogenizers 71a, 71b, and the like disposed between the focusing lenses 70a, 70b. In the emission direction of the optical system 7, a substrate stage 9 on which a substrate 8 is placed is provided. The optical system 7 is set so as to shape the pulsed laser light into a rectangle or a beam shape with a minor axis width of 1.0 mm or less.

The substrate stage 9 is movable along the surface direction (XY direction) of the substrate stage 9 and includes a scanning device 10 that moves the substrate stage 9 along the surface direction at high speed.

Next, a method for crystallizing an amorphous silicon thin film using the above-mentioned ultraviolet solid-state laser annealing apparatus 1 will be described.

First, the substrate 8 on which the amorphous silicon thin film 8 a is formed is placed on the substrate mounting table 9 . In this embodiment, the substrate 8 is not heated by a heater or the like.

A pulse signal is generated in the control circuit 2a to output a pulse laser with a preset pulse frequency (6-10kHz) and a pulse width of 5-100ns. According to the pulse signal, the ultraviolet solid-state laser oscillator 2 outputs a wavelength of 340-358nm pulsed laser.

The pulsed laser light output from the ultraviolet solid-state laser oscillator 2 reaches the attenuator 3 and passes through the attenuator 3 to be attenuated at a predetermined attenuation rate. The attenuation rate is set so that the pulsed laser beam has an energy density specified in the present invention on the processed surface. The attenuator 3 can also make the attenuation rate variable.

The pulsed laser light with adjusted energy density is transmitted through the optical fiber 5 and introduced into the optical system 7 . In the optical system 7, as described above, the pulsed laser light is shaped into a rectangle or a beam shape with a minor axis width of 1.0 mm or less by using the focusing lenses 70a, 70b, beam homogenizers 71a, 71b, etc. The substrate 8 is irradiated with an energy density of 130 to 240 mJ/cm ² .

The above-mentioned substrate stage 9 is moved along the surface of the amorphous silicon thin film 8a in the width direction of the short axis of the beam by using the scanning device 10. As a result, in a relatively wide area of the surface of the amorphous silicon thin film 8a, Scan and irradiate the aforementioned pulsed laser light. In addition, the scanning speed of the pulsed laser is set to 50 to 1000 mm/sec according to the setting of the moving speed of the scanning device at this time, and the same region of the amorphous silicon thin film 8a is irradiated with the pulsed laser at the number of irradiations of 1 to 10 times. The number of irradiations is determined based on the pulse frequency, pulse width, short-axis width of the pulsed laser, and scanning speed of the pulsed laser.

By the irradiation of the pulsed laser light, only the amorphous silicon thin film 8a on the substrate 8 is heated and polycrystallized in a short time. At this time, the heating temperature of the amorphous silicon thin film 8a is a temperature not exceeding the crystal melting point (for example, exceeding about 1000° C. to 1400° C.). In addition, the heating temperature may be set to a temperature not exceeding the amorphous melting point, or may be set to a temperature exceeding the amorphous melting point and not exceeding the crystalline melting point.

The crystal grain diameter of the crystalline thin film obtained by the above-mentioned irradiation is 50 nm or less, and the crystalline thin film has no protrusions observed in the conventional solid-phase crystal growth method, and has uniform, fine, and high-quality crystallinity. For example, an example in which the average grain size is 20 nm or less and the standard deviation is 10 nm or less is particularly mentioned. Crystal grains can be determined by atomic force microscopy (AFM). In addition, the degree of crystallinity can be calculated based on the ratio of the area of the crystalline peak to the area of the non-crystalline peak obtained by Raman spectroscopy, and the degree of crystallinity is preferably 60 to 95%.

The above-mentioned crystalline thin film can be suitably used for an organic EL display. However, the use as the present invention is not limited thereto, and it can be used as other liquid crystal displays or electronic materials.

In addition, in the above-described embodiment, the pulsed laser beam is relatively scanned by moving the substrate stage, but the pulsed laser beam may be relatively scanned by moving an optical system for transmitting the pulsed laser beam at high speed.

Example 1

Next, examples of the present invention and comparative examples are compared and described.

An experiment was conducted in which an amorphous silicon thin film formed on the surface of a glass substrate by a usual method was irradiated with pulsed laser light using the ultraviolet solid-state laser annealing apparatus 1 of the above-mentioned embodiment.

In this test, the wavelength of the pulse laser was set in the ultraviolet region of 355 nm, the pulse frequency was set to 8 kHz, and the pulse width was set to 80 nsec. Use attenuator 3 to adjust the energy density to the object energy density.

The pulsed laser beam is shaped into a circular shape on the processing surface by an optical system, the energy density, beam size, and number of irradiations on the processing surface are changed, and the pulsed laser beam is irradiated to the amorphous silicon film on the substrate. Heating amorphous silicon turns it into crystalline silicon. The film subjected to this irradiation was evaluated using the SEM photograph shown in FIG. 2 . In addition, each condition and evaluation result are shown in Table 1.

In a thin film irradiated with a pulsed laser energy density of 70 mJ/cm ² , if the number of times of irradiation is set to 8000, as shown in Photo 1, microcrystals of 10-20 nm can be produced. However, it is not industrially applicable due to the high number of irradiations and the long processing time required.

In addition, the amorphous silicon thin film was not crystallized when the energy density was 70 mJ/cm ² and the number of irradiations was 800 times. This is because the energy density was too low, and crystallization could not be induced even if the number of times of irradiation was increased.

Next, when the energy density of the pulsed laser was set to 140, 160, 180, or 200 mJ/cm ² , as shown in Photographs 2 to 6, uniform fine crystals were obtained.

Next, when the energy density of the pulsed laser was set at 250 mJ/cm ² , as shown in Photo 7, since it was heated to a temperature exceeding the crystal melting point and melted, it became a molten crystal and fine crystals could not be obtained.

Furthermore, when the energy density of the pulse laser was set at 260 mJ/cm ² , as shown in Photo 8, ablation occurred.

As described above, uniform and fine crystallization can only be achieved by setting the energy density, pulse width, and number of irradiations of the pulsed laser within appropriate ranges.

As can be seen from the above photographs, the polysilicon thin film obtained by the method of the present invention has less variation in crystal grain diameter, the entire surface of the polysilicon thin film is uniformly polycrystallized, and the polysilicon thin film is a high-quality polysilicon thin film. In addition, at the same time, it was confirmed that the same uniform crystallites were also formed in the stacked portion. Since a crystalline silicon film can be obtained uniformly with crystal grains as small as 50 nm or less without generating protrusions, it is obvious that a silicon film with less variation in TFT characteristics can be provided.

[Table 1]

Next, other examples of the present invention will be described in comparison with comparative examples.

An experiment was conducted in which an amorphous silicon thin film formed on the surface of a glass substrate by a usual method was irradiated with pulsed laser light using the ultraviolet solid-state laser annealing apparatus 1 of the above-mentioned embodiment. In this test, the wavelength of the pulse laser was set in the ultraviolet region of 355 nm, the pulse frequency was set to 6 to 8 kHz, and the pulse width was set to 80 ns (nsec). Use the attenuator 3 to adjust the pulse fluence to the object fluence. Use the stage rate to adjust the number of shots to be the number of shots for the object. Table 2 shows the energy density and irradiation times of each test material. In addition, Table 2 also shows the crystallinity measured below.

The pulsed laser beam is shaped into a rectangle on the processing surface by an optical system, and the pulsed laser beam is irradiated on the amorphous silicon on the substrate. Heating amorphous silicon turns it into crystalline silicon. The irradiated thin film was evaluated using the SEM photographs shown in FIGS. 3 and 4 and Raman spectrometry as shown in the example in FIG. 5 . The degree of crystallinity is based on the Raman spectroscopic measurement results, and the crystallized Si peak area/(amorphous Si peak area+crystallized Si peak area) is calculated according to the following formula (1).

In the following examples and comparative examples, specifically, an Ar ion laser with a wavelength of 514.5 nm and an output of 2 mW was focused to 1 mmφ, and a thin film with a thickness of 50 nm was irradiated with the Ar ion laser to perform Raman spectroscopy. It can be seen from the Raman measurement results in Fig. 5 that Si has a sharp peak around 520 cm ^-1 , but amorphous Si has almost no peak around 480 cm ^-1 .

In addition, based on the measurement results, Gaussian fitting using the least square method was used to separate into two peak waveforms, and the crystallinity was calculated from the two peak waveforms according to the calculation formula (1).

The example shown in Fig. 5 is the data of the following Example No. 3, and the crystallinity is about 88% based on the result of the above calculation.

(Example 2)

In a thin film irradiated with a pulsed laser with an energy density of 130 mJ/cm ² and a pulse frequency of 6 kHz, if the number of times of irradiation is set to 6, as shown in Photo 10, a film with a diameter of Microcrystals of 10-20nm. When the degree of crystallinity was evaluated by Raman spectrometry, it was 85%. In addition, the same result can be obtained by setting the pulse frequency to 8kHz.

(Example 3)

In a thin film irradiated with pulsed laser light at an energy density of 140 mJ/cm ² and a pulse frequency of 6 kHz, if the number of times of irradiation is set to 6, as shown in Photo 11, 10 to 10 20nm crystallites. When the degree of crystallinity was evaluated by Raman spectroscopy, it was 88%. In addition, the same result can be obtained by setting the pulse frequency to 8kHz.

(Example 4)

In a thin film irradiated with pulsed laser light at an energy density of 150 mJ/cm ² and a pulse frequency of 6 kHz, if the number of times of irradiation is set to 6, as shown in Photo 12, 10 to 100 20nm crystallites. When the degree of crystallinity was evaluated by Raman spectroscopy, it was 90%. In addition, the same result can be obtained by setting the pulse frequency to 8kHz.

(Example 5)

In a thin film irradiated with a pulsed laser with an energy density of 160 mJ/cm ² and a pulse frequency of 6 kHz, if the number of times of irradiation is set to 6, as shown in Photo 13, 20 to 20 30nm crystallites. When the degree of crystallinity was evaluated by Raman spectroscopy, it was 90%. In addition, the same result can be obtained by setting the pulse frequency to 8kHz.

(Example 6)

In a thin film irradiated with a pulsed laser with an energy density of 180 mJ/cm ² and a pulse frequency of 6 kHz, if the number of times of irradiation is set to 6, as shown in Photo 14, 20 to 20 30nm crystallites. When the degree of crystallinity was evaluated by Raman spectroscopy, it was 95%. In addition, the same result can be obtained by setting the pulse frequency to 8kHz.

(Example 7)

In a thin film irradiated with pulsed laser light at an energy density of 200 mJ/cm ² and a pulse frequency of 6 kHz, if the number of times of irradiation is set to six, as shown in Photo 15, 40 to 40 50nm crystallites. When the degree of crystallinity was evaluated by Raman spectroscopy, it was 95%. In addition, the same result was obtained even if the pulse frequency was set to 8 kHz.

(comparative example 1)

In a thin film irradiated with pulsed laser light at an energy density of 250 mJ/cm ² and a pulse frequency of 6 kHz, when the number of times of irradiation is set to six, the film is heated to When the temperature exceeds the melting point, it becomes a molten crystal, so that a uniform crystal cannot be obtained. When the degree of crystallinity was evaluated by Raman spectroscopy, it was 97%. In addition, the same result was obtained even if the number of irradiations was reduced to 1 time.

(comparative example 2)

In the thin film irradiated with pulsed laser light at an energy density of 260 mJ/cm ² and a pulse frequency of 6 kHz, ablation occurred as shown in Photograph 17 when the number of times of irradiation was 6.

(comparative example 3)

In a thin film irradiated with pulsed laser light at an energy density of 120 mJ/cm ² and a pulse frequency of 8 kHz, crystallization occurred when the number of times of irradiation was set to 8, but when Secco etching was performed, Then, as shown in Photo 18, all parts of the crystal are etched. When the degree of crystallinity was evaluated by Raman spectrometry, it was 54%.

(Embodiment 8)

In a thin film irradiated with a pulsed laser with an energy density of 160 mJ/cm ² and a pulse frequency of 8 kHz, if the number of times of irradiation is set to 2, as shown in Photo 19, 10 to 100 20nm crystallites. When the degree of crystallinity was evaluated by Raman spectroscopy, it was 75%.

(Example 9)

In a thin film irradiated with a pulsed laser with an energy density of 180 mJ/cm ² and a pulse frequency of 8 kHz, if the number of times of irradiation is set to 2, as shown in Photo 20, 10 to 10 20nm crystallites. When the degree of crystallinity was evaluated by Raman spectrometry, it was 78%.

(comparative example 4)

The same experiment was performed using a XeCl excimer laser light having a wavelength of 308 nm and a pulse width of 20 nsec, which was different from the above experiment. In a thin film irradiated with pulsed laser light at an energy density of 180 mJ/cm ² and a pulse frequency of 300 Hz, if Secco etching is performed for SEM observation after eight times of irradiation and crystallization, then The entire crystallized portion is etched. When the degree of crystallinity was evaluated by Raman spectrometry, it was 54%. This is considered to be due to the fact that only the surface layer was crystallized due to the short wavelength.

(comparative example 5)

The same experiment was performed using a XeCl excimer laser light having a wavelength of 308 nm and a pulse width of 20 nsec, which was different from the above experiment. In a thin film irradiated with pulsed laser light at an energy density of 200 mJ/cm ² and a pulse frequency of 300 Hz, when the number of times of irradiation is set to 8, the film is heated to When the temperature exceeds the melting point of the crystal, it becomes a molten crystal, so that a uniform crystal cannot be obtained. When the degree of crystallinity was evaluated by Raman spectroscopy, it was 97%.

[Table 2]

In addition, in Example 3, the average grain size was 15 nm, and the standard deviation σ was 7 nm, and in Comparative Example 1, the average grain size was 72 nm, and the standard deviation σ was 42 nm.

It can be seen from the photographs in Fig. 5 and Figs. 3 and 4 that the deviation of crystal grains of the polysilicon film obtained by the present invention is small, and the ratio of crystallinity is relatively high. In addition, it was also confirmed that the entire surface was uniformly polycrystallized, and the same crystals were also formed in the superimposed part of the laser beam. Since a crystalline silicon film can be uniformly obtained with crystal grains as small as 50 nm or less without protrusions, it is possible to provide a silicon film with less variation in TFT characteristics.

As mentioned above, although this invention was demonstrated based on said embodiment and an Example, this invention is not limited to the range of the said description, Unless it deviates from the range of this invention, it cannot be overemphasized that an appropriate change is possible.

Label description

1 Ultraviolet solid-state laser annealing device

2 Ultraviolet solid-state laser oscillators

3 attenuators

4 couplers

5 fibers

6 devibration table

7 optical system

70a focusing lens

70b focusing lens

71a beam homogenizer

71b beam homogenizer

8 substrates

8a Amorphous silicon thin film

9 substrate loading table

10 scanning device

Claims (9)

1. the manufacture method of a crystalline film, it is characterised in that

Irradiate by the wavelength of 340～358nm to the amorphous silicon film overlap being present in substrate upper strata in the range of irradiating at 2～10 times That formed, have 130～240mJ/cm²The pulse laser of energy density so that amorphous silicon film is less than crystalline melt point, And described substrate is not heated, it is heated to making its crystallization become less than the temperature of crystalline melt point by described amorphous silicon film The crystallite of below 50nm.

2. the manufacture method of crystalline film as claimed in claim 1, it is characterised in that

Described amorphous silicon film is heated to less than the temperature of its fusing point or exceedes described fusing point and be less than by described pulse laser The temperature of crystalline melt point.

3. the manufacture method of crystalline film as claimed in claim 1, it is characterised in that

Described crystallization is to carry out in the range of 60～95% in degree of crystallinity.

4. the manufacture method of crystalline film as claimed in claim 1, it is characterised in that

The pulsewidth of described pulse laser is 5～100ns.

5. the manufacture method of crystalline film as claimed in claim 1, it is characterised in that

The pulse frequency of described pulse laser is 6～10kHz.

6. the manufacture method of crystalline film as claimed in claim 1, it is characterised in that

The short axis width of the pulse laser exposing to described amorphous silicon film is below 1.0mm.

7. the manufacture method of crystalline film as claimed in claim 1, it is characterised in that

Make described pulse laser described amorphous silicon film be relatively scanned and carry out described irradiation, this scanning speed be 50～ The 1000mm/ second.

8. the manufacture method of crystalline film as claimed in claim 7, it is characterised in that

Utilize optical system that described pulsed laser beam is shaped as rectangle or wire harness shape, make this optical system high-speed motion Carry out described scanning.

9. the manufacture method of the crystalline film as according to any one of claim 1 to 8, it is characterised in that

By described crystallization obtain size be below 50nm, do not have bossed crystallite.