JP4255799B2 - Method for producing crystalline silicon film - Google Patents

Description

  The present invention relates to a technique for uniformly and efficiently performing annealing over a large area, for example, as performed on a semiconductor material. The invention disclosed in the present specification also relates to a technique that does not reduce work efficiency when a specific region is irradiated with laser light while gradually changing the irradiation energy density.

  In recent years, active research has been conducted on lowering the temperature of semiconductor device processes. The main reason is that it is necessary to form a semiconductor element on an insulating substrate such as glass that is inexpensive and has high workability. In addition, there is a demand accompanying miniaturization of elements and multilayering of elements.

  In particular, a technique for forming a semiconductor element over a glass substrate is required for manufacturing a panel constituting an active matrix liquid crystal display device. This is a configuration in which thin film transistors are arranged in a matrix of several hundreds × several hundreds or more on a glass substrate. When a glass substrate is exposed to a temperature of about 600 ° C. or higher for a long time, deformation and shrinkage appear remarkably, so that the heating temperature in the thin film transistor manufacturing process is required to be as low as possible.

  In order to obtain a thin film transistor having high electrical characteristics, it is necessary to use a crystalline semiconductor as the thin film semiconductor.

  As a method for obtaining a crystalline silicon film, a technique is known in which an amorphous semiconductor film formed by a plasma CVD method or a low pressure thermal CVD method at about 500 ° C. is crystallized by heat treatment. This heat treatment is performed by allowing the sample to stand for several hours or more in a temperature atmosphere of 600 ° C. or higher. For example, when the temperature of this heat treatment process is 600 ° C., the time required for the treatment requires 10 hours or more. Generally, when a glass substrate is heated at a temperature of 600 ° C. for 10 hours or more, deformation (strain) or shrinkage appears remarkably on the substrate. A thin film semiconductor that forms a thin film transistor has a thickness of several hundreds of nanometers and a size of several μm to several tens of μm. Therefore, deformation of the substrate becomes a cause of operation failure and variations in electrical characteristics. End up. In particular, when the area of the substrate is increased (diagonal of 20 inches or more), the deformation or shrinkage of the substrate becomes a serious problem.

  In addition, if heat treatment is performed at a temperature of 1000 ° C. or higher, crystallization can be performed in a processing time of several hours, but a general glass substrate can withstand a temperature of about 1000 ° C. even for a short time. Can not.

  When a quartz substrate is used, a heat treatment at 1000 ° C. or higher can be performed, and a crystalline silicon film having good crystallinity can be obtained. However, a quartz substrate having a large area is particularly expensive, and it is difficult to use it in a liquid crystal display device that is required to be increased in size from the viewpoint of economy.

  Under such circumstances, it is required to lower the temperature of the process for manufacturing the thin film transistor. As a technique for realizing a low temperature of this process, a technique of performing annealing by laser light irradiation is known. This laser irradiation technology is attracting attention as the ultimate low-temperature process. The laser beam can be applied only to a portion where high energy comparable to thermal annealing is required, and it is not necessary to expose the entire substrate to a high temperature. Therefore, a glass substrate can be used as the substrate.

  However, the annealing technique by laser light irradiation has a problem that the irradiation energy of laser light is not constant. This problem can be solved by using a device capable of irradiating more energy than necessary and reducing the output with a dimming device or the like. However, the problem of an increase in cost in accordance with the increase in size of the device remains.

  Even with such problems, the annealing technique by laser light irradiation is very useful in the sense that glass can be used as a substrate.

There are roughly the following two methods for irradiating laser light.
The first method uses a continuous wave laser such as an argon ion laser, and irradiates a semiconductor material with a spot beam. This is a method of crystallizing a semiconductor material by slowly solidifying it after the semiconductor material has melted due to the difference in energy distribution inside the beam and the movement of the beam.

  The second method is a method of crystallizing a semiconductor material by irradiating a semiconductor material with a high energy laser pulse using a pulsed laser such as an excimer laser, instantaneously melting and solidifying the semiconductor material.

The problem with the first method is that processing takes time. This is because the maximum energy of the continuous wave laser is limited and the size of the beam spot is at most mm square. On the other hand, in the second method, the maximum energy of the laser is very large, and therefore, mass productivity can be further increased by using a large spot of several cm ² or more.

  However, with a generally used square or rectangular beam, it is necessary to move the beam up and down and left and right to process a single large area substrate, and there is still room for improvement in terms of mass productivity.

  In this regard, the laser beam can be greatly improved by deforming the laser beam into a linear shape, making the beam width longer than the substrate to be processed, and scanning the beam.

  What remains as a problem to be improved is the uniformity of the laser irradiation effect. In order to improve this uniformity, the following measures are taken. One contrivance is to reduce the variation in the linear beam by making the shape of the distribution of the beam as close as possible to a rectangle by using a slit. In the above technique, in order to further reduce the non-uniformity, preliminary irradiation with weaker pulse laser light (hereinafter referred to as preliminary irradiation) is performed before irradiation with strong pulse laser light (hereinafter referred to as main irradiation). To improve the uniformity. This effect is very high and the characteristics of the semiconductor device can be remarkably improved.

  The above-described two-stage irradiation method is effective because a film of a semiconductor material containing a lot of amorphous parts has a property that the absorption rate of laser energy is significantly different from that of a polycrystalline film. It is. For example, a general amorphous silicon film (a-Si film) contains about 20 to 30 atomic% of hydrogen inside, and when suddenly irradiated with laser light having strong energy, hydrogen is ejected from the inside. As a result, the surface becomes rough and has unevenness of several tens nm to several hundreds nm. Since a thin film semiconductor used for a thin film transistor has a thickness of about several hundreds of nanometers, the surface having unevenness of several tens to several hundreds of nm is a major cause of variations in electrical characteristics.

  However, when the above two-stage irradiation is performed, a process in which a certain amount of hydrogen is desorbed by the first weak preliminary irradiation and crystallization is performed by the next main irradiation proceeds. Here, in the pre-irradiation, since the irradiation energy is not so high, the roughness of the film surface due to the rapid blow-off of hydrogen does not cause much problem.

  By these two ideas, the uniformity of the laser irradiation effect can be considerably improved. However, when the two-stage irradiation method as described above is used, the laser processing time is doubled, resulting in a decrease in throughput. In addition, since the laser is a pulse laser, a slight difference occurs in the effect of laser annealing depending on how the main irradiation and the preliminary irradiation overlap. This difference greatly affects the characteristics of the thin film transistor having a size of about several tens of μm square.

  In addition, in general, in processing technology by laser light irradiation (processing technology by altering various materials or applying laser energy), there are cases where it is desired to irradiate by changing the laser light irradiation energy multiple times in a predetermined area. . For example, the above-described annealing technique for the silicon film is one of them.

  Conventionally, in such a technique, a method of irradiating a laser beam in a plurality of times has been adopted. However, dividing the laser light irradiation into a plurality of times results in a significant reduction in work efficiency because the processing time is doubled. Also, irradiating laser light to a specific irradiation area in multiple times is likely to cause a problem of misalignment of the area irradiated with laser light, which is technically difficult or expensive. May be required and was not practical.

  In the invention disclosed in this specification, it is an object to solve the problem of non-uniformity of the annealing effect upon laser light irradiation. It is another object of the present invention to improve the economic efficiency at the time of laser light irradiation.

  In the invention disclosed in this specification, the above-described problems are solved by devising the distribution of the linear laser beam. That is, in the invention disclosed in this specification, the distribution of the linear laser beam is formed into a shape like a normal distribution, for example. The laser beam having such an energy distribution is irradiated while scanning on the semiconductor material. Then, in the laser irradiation method that performs the preliminary irradiation and the main irradiation described above, the role of the weak laser energy of the preliminary irradiation is played by the portion of the energy distribution (normal distribution) from the middle of the mountain to the bottom of the mountain. The same effects as those obtained when two-stage or multi-stage laser irradiation is performed by laser irradiation can be obtained.

However, in order to obtain the required annealing effect, it is preferable to perform laser irradiation after satisfying specific conditions. The conditions are listed below.
(1) A silicon film having a thickness of 15 to 100 nm is used as an irradiation target.
(2) A linear laser beam having a pulse width of N oscillations per second and having a normal distribution with a width L or a beam profile (beam shape) equivalent thereto is used.
(3) Irradiate the surface to be irradiated with scanning with a laser beam at a velocity V in a direction having a normal distribution.
(4) The average energy density per pulse is set to 100 to 500 mJ / cm ² .
(5) Laser light irradiation is performed under conditions satisfying 10 ≦ (LN / V) ≦ 30.

  Under the above conditions, a silicon film having a thickness of 15 to 100 nm is an object to be irradiated. If the thickness is 15 nm or less in experimental annealing of a silicon film, the uniformity of film formation In addition, there is a problem in the uniformity of the annealing effect and also in the reproducibility, and when the thickness is 100 nm or more, it is not practical because it is required to increase the output of the laser beam and is used for a thin film transistor This is because such a thickness is not required as the thickness of the crystalline silicon film.

The energy density per pulse is set to 100 to 500 mJ / cm ² , experimentally, in laser annealing for a silicon film having a thickness of 100 nm or less, laser light is irradiated at an energy density of 100 to 500 mJ / cm ^2. This is because it has been proved to be effective. This energy density is defined as the value of the top portion of a beam profile having a normal distribution or a similar shape.

  In the above configuration, the parameter indicated by LN / V is a single scan of a linear pulsed laser beam having a beam profile whose energy density distribution in the width direction conforms to (or can be considered as a normal distribution) or a normal distribution. In this case, the number of pulses irradiated to one specific linear region is shown.

Each invention disclosed in this specification will be described below.
One of the inventions disclosed in this specification is:
Forming an amorphous silicon film;
Holding a metal element for promoting crystallization of silicon on the surface of the amorphous silicon film;
Heating the amorphous silicon film to form a crystalline silicon film;
A method for producing a crystalline silicon film by processing a pulsed laser into a linear beam and irradiating the crystalline silicon film with the linear beam,
In the linear beam, the energy distribution in a cross section parallel to the scanning direction of the laser beam is a normal distribution or a distribution similar to a normal distribution,
When scanning the crystalline silicon film along the scanning direction of the laser beam using the linear beam, by irradiating the crystalline silicon film while overlapping a part of the linear beam The point of the crystalline silicon film is irradiated with the linear beam 3 to 100 times.

  The above-described configuration is characterized in that the laser beam is irradiated over a specific region a plurality of times by irradiating the laser beam processed into a linear shape.

Other aspects of the invention are:
Forming an amorphous silicon film;
Holding a metal element for promoting crystallization of silicon on the surface of the amorphous silicon film;
Heating the amorphous silicon film to desorb hydrogen;
Heating the amorphous silicon film to form a crystalline silicon film;
A method for producing a crystalline silicon film by processing a pulsed laser into a linear beam and irradiating the crystalline silicon film with the linear beam,
In the linear beam, the energy distribution in a cross section parallel to the scanning direction of the laser beam is a normal distribution or a distribution similar to a normal distribution,
When scanning the crystalline silicon film along the scanning direction of the laser beam using the linear beam, by irradiating the crystalline silicon film while overlapping a part of the linear beam The point of the crystalline silicon film is irradiated with the linear beam 3 to 100 times.

Other aspects of the invention are:
The crystalline silicon film includes a metal element at a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁹ atoms / cm ³ .

Other aspects of the invention are:
The amorphous silicon film has a thickness of 15 to 100 nm.

Other aspects of the invention are:
The linear beam has an average energy density per pulse of 100 to 500 mJ / cm ² , or the length of the linear beam in the scanning direction is a portion where the energy of the laser beam is 5% or more of the maximum energy. Or a pulse oscillation type laser is an excimer laser.

  When this configuration is adopted, it is possible to irradiate a specific region with laser light whose energy density is gradually changed n times. In the above configuration, the irradiation energy profile of the laser beam is not limited to a normal distribution, and may be, for example, a beam shape in which the energy density is changed stepwise. It may also have a triangular energy profile.

  For example, when a linear laser beam having a normal distribution in the width direction as shown in FIG. 3 is irradiated while scanning in the width direction after satisfying certain conditions, the weak energy at the bottom of the initial energy distribution Is gradually irradiated with strong energy. And after irradiation of a fixed value is performed, irradiation energy becomes weak gradually and irradiation is complete | finished.

For example, a linear pulsed laser beam whose irradiation energy has a normal distribution in the width direction is used, the beam width is L, the number of oscillations per second is N, the scanning speed is V, and LN / V = In the case of 15, the pulse is irradiated 15 times in one linear region by one scanning of the laser beam. These 15 irradiations are performed one after another at an energy density corresponding to 15 divided normal distributions. For example, a specific linear region (the width of the linear region is considerably narrow) is successively irradiated with pulsed laser light having an energy density of E _{1 to} E ₁₅ as shown in FIG. The Rukoto. At this time, the irradiation energy density of the laser pulses E _{1 to} E ₈ gradually increases as they are irradiated, and the irradiation energy of the E _{8 to} E ₁₅ laser pulses gradually increases as they are irradiated. Density decreases.

  Thus, the process of gradually irradiating the irradiation energy gradually from the weak energy irradiation and further gradually decreasing the irradiation energy can obtain a predetermined annealing effect while suppressing the roughening of the surface of the silicon film. In addition, since a predetermined effect can be obtained by one-time laser irradiation while scanning instead of irradiating the laser beam in a plurality of times, high working efficiency can be obtained.

  In particular, by using a laser beam whose energy density is continuously changed, it is possible to obtain the same effect as when irradiation is performed while changing energy in multiple steps. Such an action can be said similarly except for the annealing effect on the silicon film.

  With the laser irradiation technique of the invention disclosed in this specification, mass productivity can be improved and uniformity of a film to be a semiconductor device can be improved. The invention disclosed in this specification can be used for all laser processing processes used in the process of semiconductor devices. In particular, when used as a semiconductor device in a thin film transistor manufacturing process, high characteristics and good uniformity are obtained. be able to. Further, in the case where laser beams having different irradiation energy densities are irradiated to a predetermined region in multiple stages, laser irradiation can be performed in a state where the overlap of laser beams is not shifted. This has a great effect on the uniformity of the characteristics of the elements when manufacturing semiconductor devices.

  Further, in the step of gradually changing the energy density of the laser light irradiated to a predetermined region in a plurality of times of irradiation, the working efficiency can be greatly improved by utilizing the configuration disclosed in this specification. In other words, without irradiating laser beams with different energy densities in multiple steps as in the past, the irradiation energy density is changed stepwise by irradiating while scanning one laser beam. The same effect as that obtained can be obtained.

  In this embodiment, a silicon film is used as a semiconductor material. In the process of increasing the crystallinity of this film by irradiating a laser beam to a silicon film or silicon compound film in an amorphous state or crystallinity, the homogeneity of the film surface tends to decrease. The following shows an example in which the reduction can be suppressed as much as possible, and the laser irradiation processing time can be shortened compared to the case of the two-stage laser irradiation described in [Prior Art], and the same or higher effect can be obtained. .

  First, the apparatus will be described. FIG. 1 shows a conceptual diagram of a laser annealing apparatus used in this embodiment. The main structure of this laser annealing apparatus is arranged on a table 1. Laser light is oscillated by an oscillator 2. The laser light oscillated by the oscillator 2 is a KrF excimer laser (wavelength 248 nm, pulse width 25 ns). Of course, other excimer lasers and even other types of pulsed lasers can be used.

  The laser light oscillated by the oscillator 2 is amplified by the amplifier 3 via the total reflection mirrors 5 and 6 and further introduced into the optical system 4 via the total reflection mirrors 7 and 8.

The laser beam just before entering the optical system 4 has a rectangular shape of about 3 × 2 cm ² , but the optical system 4 converts the beam into a narrow beam (linear beam) having a length of about 10 to 30 cm and a width of about 0.1 to 1 cm. Processed. As shown in FIG. 3, the linear laser beam has a beam profile having a substantially normal distribution in the width direction. The energy of the laser beam that has passed through the optical system 4 is 1000 mJ / shot at the maximum.

  The reason why the laser beam is processed into such an elongated beam is to improve the processability. That is, the linear beam exits the optical system 4 and then irradiates the sample 11 through the total reflection mirror 9. Here, since the width of the beam is longer than the width of the sample 11, the entire sample can be irradiated with laser light by moving the sample in one direction. Therefore, the sample stage and the driving device 10 have a simple structure and are ready for maintenance. In addition, positioning operation (alignment) when setting the sample is easy.

  The stage 10 of the sample irradiated with the laser beam is controlled by a computer and designed to move in a direction perpendicular to the linear laser beam. Furthermore, if the table on which the substrate is placed has a function of rotating within the table surface, it is convenient for changing the scanning direction of the laser beam. A heater is built under the stage 10 so that the sample can be kept at a predetermined temperature when the laser beam is irradiated.

  An example of the optical path inside the optical system 4 is shown in FIG. The laser light incident on the optical system 4 passes through the cylindrical concave lens A, the cylindrical convex lens B, the lateral fly-eye lenses C and D, and further passes through the cylindrical convex lenses E and F to correspond to the mirror G (corresponding to the mirror 9 in FIG. 1). ) Through the cylindrical lens H, and the sample is irradiated. By moving the lens H up and down relatively with respect to the irradiation surface, the shape of the laser beam distribution on the irradiation surface can be changed from a shape close to a rectangle to a shape close to a normal distribution. The total reflection mirror G in FIG. 2 corresponds to the total reflection mirror 9 in FIG. Therefore, the lens H is actually disposed between the total reflection mirror 9 and the sample 11.

  Hereinafter, an example in which a crystalline silicon film is formed over a glass substrate by laser light irradiation using the invention disclosed in this specification will be described. First, a 10 cm square glass substrate (for example, Corning 7059 glass substrate or Corning 1737 glass substrate) is prepared. A silicon oxide film having a thickness of 200 nm is formed on the glass substrate by plasma CVD using TEOS as a raw material. This silicon oxide film functions as a base film that prevents impurities from diffusing into the semiconductor film from the glass substrate side.

  Next, an amorphous silicon film (amorphous silicon film) is formed by plasma CVD or low pressure thermal CVD. Although the plasma CVD method is used here, a low pressure thermal CVD method may be used. Note that the thickness of the amorphous silicon film is 50 nm. When annealing is performed by laser light irradiation to obtain a crystalline silicon film, the starting amorphous silicon film is preferably 100 nm or less in thickness. This is because if the film thickness is 100 nm or more, a predetermined annealing effect cannot be obtained.

  Thus, an amorphous silicon film formed on the glass substrate can be obtained. Next, using the apparatus shown in FIG. 1, the silicon film having crystallinity is irradiated with a KrF excimer laser (wavelength 248 nm, pulse width 25 ns). A crystalline silicon film can be obtained by this laser light irradiation.

  The laser beam is shaped into a linear shape using a beam shape conversion lens, and the beam area at the irradiated portion is set to 125 mm × 1 mm. Note that the end of the beam is unclear because the beam profile of the linear laser is normally distributed. Therefore, in this case, a portion having 5% or more of the maximum energy in the beam profile is defined as a beam.

The sample is placed on the stage 10, and the entire surface is irradiated by moving the stage at a speed of 2 mm / s. The laser light irradiation conditions are such that the energy density of the laser light is 300 mJ / cm ² and the number of pulses (number of pulse oscillations per second) is 30 pulses / s. Here, the energy density refers to the density of the peak portion of the peak of the beam formed in a shape close to a normal distribution.

When the above conditions are applied, V = 2 × 10 ⁻³ (m / s), N = 30 (1 / S), and L = 1 × 10 ⁻³ (m), so (LN / V) = 15, which satisfies the conditions disclosed in this specification.

When laser irradiation is performed under the above-described conditions, when attention is paid to one point (linear region) of the sample, laser irradiation is performed in 15 stages. The energy densities of the 15-stage pulses correspond to the energy densities E _{1 to} E ₁₅ of the normal distribution shown in FIG. When linear laser light is irradiated under the above conditions, laser pulses with energy densities E _{1 to} E ₁₅ are sequentially irradiated onto a linear region of 125 mm × 1 mm.

  FIG. 3 shows how the linear laser light is irradiated while being scanned. For example, when attention is paid to the region indicated by the line A, it can be seen that a pulse having a high energy density is gradually irradiated from a pulse having a weak energy density corresponding to the bottom portion of the normal distribution. When attention is paid to the region indicated by the line B, it can be seen that a pulse having a small energy density is gradually irradiated after the laser pulse having the maximum energy density at the top of the normal distribution is irradiated.

According to the experiments by the present inventors, it has been found that the best crystalline silicon film can be obtained when the value indicated by (LN / V) is 10-30. In other words, it has been found that it is optimal to crystallize a silicon film so that a predetermined linear region is irradiated 10 to 30 times. The energy density of the irradiated laser beam is in the range of 100 to 500 mJ / cm ² , preferably in the range of 300 to 400 mJ / cm ² .

  Note that the substrate temperature is kept at 200 ° C. during the laser light irradiation. This is performed in order to moderate the rise and fall speeds of the substrate surface temperature due to laser light irradiation. In general, it is known that an abrupt change in the environment impairs the uniformity of a substance. However, by keeping the substrate temperature high, deterioration of the uniformity of the substrate surface due to laser irradiation is suppressed as much as possible. In this embodiment, the substrate temperature is set to 200 degrees, but in the actual implementation, the optimum temperature for laser annealing is selected from 100 degrees to 600 degrees. Further, the atmosphere control is not particularly performed, and irradiation can be performed in the air.

  In this embodiment, an example is shown in which laser light is first irradiated to a crystalline silicon film that has been crystallized by heating to further improve its crystallinity and homogeneity. According to studies by the present inventors, it has been found that a crystalline silicon film can be obtained by heat treatment at 550 ° C. for about 4 hours by using a metal element that promotes crystallization of silicon. This technique is described in JP-A-6-232059 and JP-A-6-244103.

By utilizing the above technique, a crystalline silicon film can be obtained in a temperature range where distortion or the like is not a problem even with a large-area glass substrate. By manufacturing a thin film transistor using this crystalline silicon film, it is possible to obtain a film whose characteristics are dramatically improved as compared with a thin film transistor using a conventional amorphous silicon film. Specifically, a thin film transistor using an amorphous silicon film has a mobility of 1 (cm ² / Vs) or less. However, when a crystallization technique using the metal element is used, the mobility is several tens (cm ² / Vs) or higher mobility can be obtained.

  However, it has been clarified from observation by electron micrographs and observation by Raman spectroscopy that many amorphous components remain in the crystalline silicon film obtained by using the above technique. It has been found that the characteristics of the obtained thin film transistor can be further improved by crystallizing the remaining amorphous component by laser light irradiation.

A manufacturing process of the crystalline silicon film described in this embodiment will be described below. First, a silicon oxide film as a base film is formed to a thickness of 200 nm on a glass substrate. Next, an amorphous silicon film is formed to a thickness of 50 nm by plasma CVD. Then, a nickel acetate solution is applied to the surface of the amorphous silicon film using a spin coater. The concentration of nickel element in the nickel acetate solution is adjusted so that the concentration of nickel element remaining in the silicon film finally becomes 1 × 10 ^{16 to} 5 × 10 ¹⁹ cm ⁻³ . When the concentration is higher than this range, the properties as a metal silicide appear. Moreover, it is because the effect which promotes crystallization is not acquired as it is below this concentration range. The nickel element concentration is defined as the maximum value measured by SIMS (secondary ion analysis).

  As a metal element that promotes crystallization of silicon, nickel is most useful in terms of reproducibility and effects. However, one or more elements selected from Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au can be used. In particular, Fe, Cu, Pd, and further Pt can provide an effect that is sufficiently practical.

  Once the surface of the amorphous silicon film is held in contact with nickel element, the hydrogen in the amorphous silicon film is released by holding it at 450 ° C. for 1 hour in a nitrogen atmosphere. . This heat treatment is for intentionally forming a dangling bond in the amorphous silicon film to lower the threshold energy for subsequent crystallization.

  Next, in a state where the nickel element is held in contact with the surface of the amorphous silicon film, heat treatment is performed to transform the amorphous silicon film into a crystalline silicon film. This heat treatment step is performed at 550 ° C. for 4 hours. Although this heat treatment can be performed at a temperature of 500 ° C. or higher, it is important to set the temperature below the strain point of the glass substrate.

  Thus, a crystalline silicon film can be obtained on the glass substrate. Then, laser light is irradiated by the same method and conditions as shown in the first embodiment. In this laser light irradiation step, a crystalline silicon film with further enhanced crystallinity and uniformity can be obtained. In addition, it has been proved by experiment that the energy density of the laser beam can be improved by increasing the energy density by 20% to 50% compared to the case of Example 1.

  As in this example, a technique for improving the crystallinity of a crystalline silicon film obtained by heating using a metal element that promotes crystallization of silicon by further irradiating laser light is As a result, it is possible to obtain a film having excellent crystallinity, uniformity, and productivity as compared with the obtained crystalline silicon film only by laser light irradiation.

  In addition, when a laser beam is irradiated to a crystalline silicon film crystallized by heating from the introduction of a metal element such as nickel, a phenomenon such as segregation or partial aggregation of the metal element occurs. It will be seen. Such segregation or partial agglomeration of the metal element becomes a trap center, and therefore, when used for a semiconductor device, the electrical characteristics thereof are greatly reduced. However, such a phenomenon is not observed when the laser light irradiation method disclosed in this specification is employed. This is because it is possible to suppress the segregation and partial aggregation of the metal element by gradually applying weak laser energy step by step.

An outline of an apparatus for irradiating laser light is shown. An optical system for processing laser light into a linear shape is shown. The state in the case of scanning and irradiating linear laser light having a normal distribution is shown. The outline of the beam profile of the energy intensity of a linear laser beam is shown.

Explanation of symbols

1 unit 2 Laser starter 3 Amplifier 4 Optical system 5 Total reflection mirror 6 Total reflection mirror 7 Total reflection mirror 8 Total reflection mirror 10 Sample stage moving mechanism 11 Sample

Claims (6)

Forming an amorphous silicon film;
Holding a metal element for promoting crystallization of silicon on the surface of the amorphous silicon film;
Heating the amorphous silicon film to desorb hydrogen;
Heating the amorphous silicon film to form a crystalline silicon film;
A method for producing a crystalline silicon film by processing a pulsed laser into a linear beam and irradiating the crystalline silicon film with the linear beam,
The linear beam, the energy distribution at a cross section parallel to the scanning direction of the laser beam is a normal distribution,
When scanning the crystalline silicon film along the scanning direction of the laser beam using the linear beam, by irradiating the crystalline silicon film while overlapping a part of the linear beam A method for producing a crystalline silicon film, wherein one point of the crystalline silicon film is irradiated with the linear beam 3 to 100 times. 2. The method for manufacturing a crystalline silicon film according to claim 1, wherein the crystalline silicon film contains the metal element at a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁹ atoms / cm ³ .   3. The method for manufacturing a crystalline silicon film according to claim 1, wherein the amorphous silicon film has a thickness of 15 to 100 nm. 4. The method for manufacturing a crystalline silicon film according to claim 1, wherein the linear beam has an average energy density per pulse of 100 to 500 mJ / cm ^{2. 5} .   5. The crystalline silicon film according to claim 1, wherein the length of the linear beam in the scanning direction is a length of a portion where the energy of the laser beam is 5% or more of the maximum energy. Manufacturing method.   6. The method for manufacturing a crystalline silicon film according to claim 1, wherein the pulsed laser is an excimer laser.

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