JP2003332400A - Method and system for calculating mobility of semiconductor thin film, method and system for crystallization laser annealing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To monitor the mobility of a semiconductor thin film with high accuracy even in the case of inprocess. <P>SOLUTION: A mobility monitoring section 34 comprises a light emitting section 36 and a reflected light receiving section 38 disposed above a substrate carrying passage on the downstream side of a laser irradiating position PA for annealing, a transmitted light receiving section 40 disposed below the substrate carrying passage, and a section 42 for calculating the mobility of the semiconductor thin film (poly-Si film) being measured based on the output signals from both light receiving sections 38 and 40. A process control section 44 controls each section in the system, especially the process parameters at a laser light source 26 or the substrate carrying passage, based on the results of monitoring (mobility) from the mobility monitoring section 34. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to a technique for calculating the mobility of a semiconductor thin film and a technique for recrystallizing an amorphous Si film with a laser to form a polycrystalline Si film.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display (LCD)
A polycrystalline Si film has been put into practical use as a material for a thin film transistor (TFT) in the above. Since the mobility of the polycrystalline Si film is several tens to 100 cm ² / V · s or higher, which is orders of magnitude higher than that of the amorphous Si film, it is suitable for a large-screen display that requires high-speed operation. The peripheral drive circuit can also be mounted on the display substrate in the form of SiTFT. There are a high temperature process and a low temperature process in the manufacturing process of the polycrystalline Si film. The high temperature process requires a quartz substrate having a high heat resistant temperature. Therefore, the development of low-temperature processes that can use glass substrates is expected,
Of these, the crystallization laser annealing method of forming a polycrystalline Si film by melting and recrystallizing an amorphous Si film with a laser has been drawing attention.

The crystallization laser annealing method generally uses an excimer laser and irradiates an amorphous Si film on a glass substrate with a long or line-shaped laser beam to obtain S.
The i film is instantaneously melted and crystallized in the cooling process. By moving the substrate in the direction orthogonal to the laser beam length direction, the entire surface of the amorphous Si film can be converted into a polycrystalline Si film. At the time of crystallization, in order to improve the grain boundary characteristics of the polycrystalline Si film, a magnetic field is also applied together with laser beam irradiation.

[0004]

The polycrystalline Si film formed by the laser annealing method as described above has different mobilities depending on the size of crystal grains. Generally, the larger the particle size, the higher the mobility, and 100 cm ² / V with a particle size of 0.3 μm.
· S or more mobility can be obtained, the particle size of about 1.5μm when n-type 200 cm ² / V · s or more mobility in the TFT is obtained. Since the mobility of the polycrystalline Si film is an important characteristic value that determines the operating speed of the TFT, it needs to be controlled during the TFT manufacturing process. However, conventionally, there has been no non-contact type mobility monitoring technology capable of measuring or calculating the mobility of a polycrystalline Si film in-situ or in-process with high accuracy.

In the conventional crystallization laser annealing method, excimer laser light having a wavelength of 248 nm or 308 nm is adopted because the absorptivity of the amorphous Si film is high. However, when the excimer laser light in such a wavelength region is not completely absorbed by the amorphous Si film, the excimer laser light may enter the glass substrate to melt or damage the substrate. Recent boards are becoming thinner and thinner.
There is a demand for a crystallization laser annealing technique capable of efficiently forming a polycrystalline Si film while avoiding damage to the substrate as it becomes large and easily cracked.

On the other hand, in the excimer laser beam in the wavelength range as described above, the reflectance after the amorphous Si is melted, that is, the reflectance of liquefied Si is increased, laser energy does not penetrate into the inside, and the Si film There is also a problem that it is difficult to melt deeply enough.

Further, in the conventional method of applying a magnetic field in the crystallization laser annealing method, the crystal orientations of crystal grains are aligned,
Although effective for improving the grain boundary characteristics, there are problems that a large-scale magnetic field generator is required and it is difficult to efficiently realize grain coarsening of crystals.

The present invention has been made in view of the above-mentioned problems of the prior art, and the mobility calculation for a non-contact type semiconductor thin film capable of monitoring the mobility of the semiconductor thin film with high accuracy even in the process. It is an object to provide a method and a device.

Another object of the present invention is to provide a semiconductor manufacturing apparatus capable of performing highly accurate process control by feeding back the mobility of a semiconductor thin film in-process.

Another object of the present invention is to provide a crystallization laser annealing method for obtaining a highly reliable polycrystalline Si film by melting and recrystallizing an amorphous Si film well without damaging a glass substrate. To provide.

Another object of the present invention is to fully melt the entire Si film by making the laser energy reach a deep layer even after the surface of the Si film is melted or liquefied, and to obtain a polycrystalline Si film having good film quality. Another object of the present invention is to provide a crystallization laser annealing method to be obtained.

Another object of the present invention is to provide a crystallization laser annealing method and apparatus capable of improving crystal grain coarsening of a polycrystalline Si film by an efficient magnetic field application method.

[0013]

In order to achieve the above object, the mobility calculating method for a semiconductor thin film of the present invention irradiates a semiconductor thin film formed on a substrate with a light beam having a predetermined wavelength. Measuring the reflectance and the transmittance, and the step of obtaining the mobility of the semiconductor thin film from a predetermined arithmetic expression based on the reflectance and the transmittance.

Further, the mobility calculating device for a semiconductor thin film of the present invention includes a light beam irradiation means for irradiating a semiconductor thin film formed on a substrate with a light beam having a predetermined wavelength, and the light from the semiconductor thin film. Reflectance measuring means for receiving the reflected light corresponding to the beam and measuring the reflectance, and transmittance measuring means for receiving the transmitted light corresponding to the light beam from the semiconductor thin film and measuring the transmittance, And a mobility calculating means for calculating the mobility of the semiconductor thin film based on the reflectance and the transmittance.

In the mobility calculating method and the mobility calculating apparatus of the present invention, since the reflectance and the transmittance of the semiconductor thin film are measured by using the light beam and the mobility is calculated, the non-contact type in-process method is used. Mobility monitoring can be performed.

In the present invention, when the semiconductor thin film to be monitored is a polycrystalline Si film, the wavelength of the light beam is preferably in the range of 0.2 μm to 0.4 μm, 0.3
The vicinity of μm is most suitable.

The semiconductor manufacturing apparatus of the present invention comprises a semiconductor thin film forming means for forming a semiconductor thin film on a substrate, a mobility calculating apparatus of the present invention for calculating the mobility of the semiconductor thin film, and the mobility calculating apparatus. And a process control means for controlling a predetermined process parameter in the semiconductor thin film forming means according to the mobility. In such a configuration, the mobility calculated by the mobility calculating apparatus of the present invention is fed back to the process control, so that the management of the semiconductor thin film manufacturing process can be improved.

The first crystallization laser annealing method of the present invention is a crystallization laser annealing method in which a semiconductor thin film formed on a substrate is melted by laser irradiation and crystallized in a cooling process to form a polycrystalline Si film. In the method, the laser light has a wavelength near or shorter than a wavelength corresponding to a plasma frequency in the melted semiconductor thin film.
In this method, when the semiconductor thin film is melted and liquefied by the laser energy, the absorption of the laser energy is further increased, so that the semiconductor thin film can be fully melted to the deep layer.

In the second crystallization laser annealing method of the present invention, a semiconductor thin film formed on a glass substrate is melted by irradiation with laser light and crystallized in a cooling process to form polycrystalline Si.
In the crystallization laser annealing method for forming a film, the laser light has a wavelength in the range of 0.4 μm to 1.0 μm. In this method, even if laser light is incident on the glass substrate through the semiconductor thin film, the laser light is absorbed almost or only slightly, so that the glass substrate is not adversely affected.

According to a third crystallization laser annealing method of the present invention, a semiconductor thin film formed on a substrate is irradiated with laser light having a linear cross section while applying a magnetic field, and the semiconductor thin film is irradiated with laser light. Melting the portion, moving the substrate relative to the laser light so that the laser irradiation portion moves from one end to the other end on the semiconductor thin film,
In a crystallization laser annealing method for melting and recrystallizing the semiconductor thin film entirely, a relatively strong magnetic field is applied to the vicinity of the boundary between the laser irradiated portion and the recrystallized portion of the semiconductor thin film and the laser irradiation of the semiconductor thin film. The magnetic field near the boundary between the portion and the laser non-irradiated portion is weakened.

Further, the crystallization laser annealing apparatus of the present invention comprises a laser irradiation means for irradiating a semiconductor thin film formed on a substrate with a laser beam having a linear cross section, and irradiating the semiconductor thin film with the laser beam. Scanning means for moving the substrate relative to the laser light so that the laser-irradiated portion receiving the laser light moves from one end to the other end on the semiconductor thin film; and the laser-irradiated portion and the recrystallized portion of the semiconductor thin film. And a magnetic field applying means for applying a relatively strong magnetic field near the boundary between the laser-irradiated portion and the non-laser-irradiated portion of the semiconductor thin film.

According to the third crystallization laser annealing method or the crystallization laser annealing apparatus, a strong magnetic field is applied near the solidification interface on which recrystallization is performed to suppress the generation of vortices in the melted portion. On the other hand, the magnetic field near the solidification interface where melting starts is weakened to allow the generation of vortices in the melted portion. As a result, the effect of the magnetic field on the melt recrystallization of the semiconductor thin film can be improved.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a TFT according to an embodiment of the present invention.
-A system configuration of a low temperature polycrystalline Si film manufacturing apparatus for LCD is shown. This system uses a cluster system,
Amorphous SiCVD apparatus 12, laser annealing apparatuses 14 and 16, insulating film CVD apparatus 18 and load lock chambers or cassette chambers 20 and 22 are provided around transfer chamber 10 functioning as a central platform.
Are arranged. The transfer chamber 10 is connected to each device or each chamber (12 to 2 through the gate valve 24).
It is possible to communicate with 2). Each chamber or the chamber of each device (10 to 22) can independently form or maintain a depressurized space at a predetermined vacuum degree. The cassette chambers 20 and 22 can be opened to atmospheric pressure when a substrate to be processed, for example, a glass substrate is loaded and unloaded, and an atmosphere of an inert gas can be formed if necessary.

In the transfer chamber 10, there is provided a transfer device (not shown) having a rotatable and expandable / contractible transfer arm configured to be able to move in and out of the peripheral devices or chambers (12 to 22). There is. In this system, the transfer device transfers the glass substrate to each device or each chamber (12 to 2) via the transfer chamber 10.
By transporting between 2), a semiconductor thin film and an insulating film can be formed on a glass substrate by an in-line low temperature process without exposing to the outside air.

A series of steps in this system (example)
Is as follows: The glass substrate carried into the transfer chamber 10 from any one of the cassette chambers 20 and 22 is first carried into the insulating film CVD apparatus 18. In this CVD apparatus 18, an insulating film such as a silicon oxide film as a base film is formed on a glass substrate by a plasma CVD method or a low pressure CVD method to have a desired film thickness, for example, 200Å
To a film thickness. The glass substrate on which the base film has been formed in this way is then transferred to the amorphous SiCVD apparatus 12. In this CVD apparatus 12, plasma C is formed on the base film.
Amorphous Si is deposited to a desired film thickness, for example, 500 Å by VD method or low pressure CVD method. Then, the glass substrate is transferred to one of the laser annealing devices 14 and 16. Laser annealing device 14 (16)
Then, the amorphous Si film on the glass substrate is melted and recrystallized by the crystallization laser annealing method to be converted into a polycrystalline Si film. The structure and operation of the annealing device 14 (16) will be described in detail later. The glass substrate that has undergone the crystallization laser annealing process is transferred to one of the cassette chambers 20 and 22 and housed in the cassette.

A controller (not shown) is provided to control the operation of each part and the whole of the system. Further, when the amorphous Si film formed by the amorphous SiCVD apparatus 12 contains a considerable amount of hydrogen, an annealing apparatus (not shown) for dehydrogenation may be provided.

As will be described later, in this system, the mobility of the polycrystalline Si film formed by the laser annealing devices 14 and 16 is monitored in-situ in a non-contact manner, and the in-line is determined on the substrate judged to be defective. The crystallization laser annealing step can be performed again in. In that case, the crystallization laser annealing step may be repeated in the annealing device 14 (16), and once the crystallization laser annealing process is carried out to the transfer chamber 10, another annealing device 16 (1) is performed.
It may move to 4) and may perform the crystallization laser annealing process of the 2nd time.

Further, in this system, it is possible not only to form an independent processing space, transfer space or storage space for each chamber and each device (10-22), but also for each part in the system except the cassette chambers 20 and 22. Since it is almost completely shielded from the outside air, it is possible to prevent particles from adhering to the glass substrate or the Si film as much as possible.
Particularly, from the amorphous Si film forming step in the amorphous SiCVD apparatus 12, the laser annealing apparatus 14 (1
6) Crystallization laser annealing step, that is, polycrystalline S
Since the i-film forming process can be safely and quickly transferred in-line, the reliability of the low temperature process method can be guaranteed.

FIG. 2 shows the main construction of the laser annealing apparatus 14 (16) and the construction of the mobility monitor and the process controller in this embodiment.

The laser annealing device 14 (16) provides a laser light source 26 for generating a laser beam LA for crystallization annealing and a glass substrate G as a substrate to be processed in a predetermined direction, for example, in order to perform the crystallization laser annealing. A substrate transfer unit (not shown) that transfers in a horizontal direction at a constant speed,
A laser optical system 28 that shapes or converts the laser beam LA from the laser light source 26 into a beam having a rectangular or linear transverse cross section and guides it to the upper surface of the glass substrate G during transportation.
And at least the laser irradiation position P _A for annealing described later.
A magnetic field forming unit (not shown) that forms a magnetic field is provided in the vicinity.

The laser light source 26 comprises, for example, an excimer laser device, and emits a pulse laser beam LA having a predetermined pulse width, pulse energy and a predetermined repetition frequency in the horizontal direction. The laser optical system 28 extends the laser beam LA from the laser light source 26 in the horizontal direction (direction perpendicular to the plane of the drawing), and an optical lens 30 having a rectangular or linear beam cross section, and this optical lens. The mirror 32 reflects the linear beam LA from 30 vertically downward toward the annealing laser irradiation position P _A set on the substrate transport path. The substrate transport unit preferably has a mechanism for supporting the substrate G in partial contact and transporting it in the horizontal direction because the light receiving unit 40 is arranged below the substrate transport path in the mobility monitor unit 34 as described later. You can do it.

Crystallization laser annealing is performed as follows.
Be seen. It was carried into the laser annealing device 14 (16)
For the glass substrate G, the amorphous SiCVD device 12
Amorphous Si by the pre-process of CVD
The film is deposited with a predetermined thickness. The glass substrate G is
Directly below the mirror 32 by the substrate transfer unit as shown in FIG.
Laser irradiation position P set to_ATo the specified transport path
Or, it is transported horizontally at a constant speed on the transport route.
On the other hand, the laser light LA for annealing from the laser light source 26
Is oscillated and output by the mirror 32 of the laser optical system 28.
Laser irradiation position P _ARectangular or linear cross section towards
The laser light LA having By this,
The amorphous Si film (a-Si) on the substrate G is a laser
Irradiation position P_AIrradiated with laser light LA at
The portion, that is, the laser irradiation portion, is instantly melted. Glass
Since the substrate G is moving in the horizontal direction, the amorphous S
The portion of the i film (a-Si) melted by the laser energy is
Laser irradiation position P in a short time _AIs cooled past the
When crystallized, it is recrystallized to become polycrystalline Si. On the whole board
Looking at it, the amorphous silicon film (a-Si) is recorded on
Laser irradiation position P_AOr the laser irradiation part is relatively the substrate
Moves at a constant speed in the opposite direction to the moving direction, and
Laser annealing scanning from the substrate to the rear edge of the substrate
Then, the polycrystalline Si film (p-
Si) is formed.

In such crystallization laser annealing, the film characteristics (particularly the mobility) of the polycrystalline Si film formed on the glass substrate G depend on the size of the crystal grains, such as laser energy, substrate moving speed, substrate temperature, etc. Is the main process parameter that affects grain. In this embodiment, the laser annealing device 14 (16) is provided with a mobility monitor 34 and a process controller 44, and the mobility monitor 34 is a polycrystalline Si film (p) formed on the glass substrate G. −
Si) mobility is calculated, and the process control unit 44 controls each unit in the apparatus based on the monitor result (mobility) from the mobility monitoring unit 34. In particular, the process in the laser light source 26, the substrate transfer unit, and the like is performed. It is designed to control parameters.

The mobility monitor 34 in this embodiment
Is a light emitting unit 36 and a reflected light receiving unit 3 which are arranged on the downstream side of the annealing laser irradiation position P _A and above the substrate transport path.
8 and a transmitted light receiving portion 40 arranged below the substrate transport path.
And a mobility calculator 42 that calculates the mobility of the semiconductor thin film (polycrystalline Si film in this embodiment) to be measured from the output signals of both the light receivers 38 and 40.

The light emitting section 36 emits a laser beam LM having a predetermined wavelength and a predetermined or known light intensity for mobility monitoring, obliquely downward toward the mobility monitoring position P _M set on the substrate transport path. It includes a light emitting device such as a semiconductor laser. Although not shown, a condenser lens for condensing the laser beam LM emitted from the light emitting element near the mobility monitoring position P _M may be provided.

The reflected light receiving unit 38 receives the azimuth where the laser beam LM is reflected at the mobility monitoring position P _M , that is, the traveling direction of the laser beam LM and the mobility monitoring position P.
It has a light receiving element, for example, a photodiode, which is arranged in an azimuth having a reflection angle equal to the incident angle of the laser beam LM in a plane including the normal line of _M. The light receiving _element receives the reflected light LM _R from the mobility monitoring position P _M and outputs an electric signal corresponding to the light intensity, that is, a reflected light detection signal S _R. The reflected light detection signal S _R is input to the mobility calculator 42. A condenser lens (not shown) for converging the reflected light LM _R from the mobility monitoring position P _M on the light receiving element may be provided.

The transmitted light receiving portion 40 has a light receiving element, for example, a photodiode, which is arranged at a position facing the light emitting element of the light emitting portion 36 with the substrate transport path interposed therebetween. Photodetection element outputs an electrical signal, that the transmitted light detection signal S _T corresponding to the light intensity by receiving the transmitted light LM _T from mobility monitoring position P _M. The transmitted light detection signal S _T is input to the mobility calculator 42. Also in the transmitted light receiving section 40,
A condenser lens (not shown) may be provided for causing the incident light converging the transmitted light LM _T from mobility monitoring position P _M on the light receiving element.

In the illustrated example, the light emitting section 36, the reflected light receiving section 38, and the transmitted light receiving section 40 are arranged in a plane parallel to the substrate moving direction, but the arrangement is not limited to this. It may be arranged, for example, in a plane orthogonal to the substrate moving direction, instead of the one.

The mobility calculating section 42 inputs the reflected light detection signal S _R from the reflected light receiving section 38 and the transmitted light detection signal S _T from the transmitted light receiving section 40, and outputs these signals S _R , S. The mobility of the polycrystalline Si film (p-Si) formed on the glass substrate G is obtained from the value of _T. The mobility calculation unit 42
It may be composed of an arithmetic circuit or a microcomputer, and as shown in FIG.
It has a transmittance calculator 52, a refractive index / absorption coefficient (extinction coefficient) calculator 54, a mobility calculator 56, a corrected mobility calculator 58, and a coefficient / constant setting unit 60. The coefficient / constant setting unit 60 gives a required coefficient or constant to each of the arithmetic units 50 to 58.

The reflectance calculator 50 calculates the light intensity (measured value or converted value) of the reflected light at the mobility monitoring position P _M from the value of the input reflected light detection signal S _R , and the light of the irradiation laser beam LM is calculated. The ratio of the light intensity of the reflected light to the intensity is obtained, and this is taken as the reflectance R.

The transmittance calculator 52 calculates the light intensity (measured value or converted value) of the transmitted light at the mobility monitoring position P _M from the value of the input transmitted light detection signal S _T , and calculates the light of the irradiation laser beam LM. The ratio of the light intensity of the transmitted light to the intensity is obtained, and this is taken as the transmittance T. The transmitted light receiving section 4
Transmitted light LM _T that is received or detected zero because those transmitted through the polycrystalline Si film (p-Si) oxide film as well and the glass substrate G, a predetermined given from the coefficient / constant setting section 60 corrects The value compensates for the error.

Refractive index / absorption coefficient (extinction coefficient) calculator 54
Is the following equation based on the reflectance R and the transmittance T obtained by the reflectance calculation unit 50 and the transmittance calculation unit 52, respectively.
By calculating (1) and (2), the polycrystalline Si film (p
The refractive index n and absorption coefficient α (or extinction coefficient k) in -Si) are obtained. n = [(2R + 2) + {(2R + 2) ² -4 (1-R) ² (1+ (αλ / 4π) ² )} ^1/2 ] / (1-R) ‥‥‥ (1) α =-(1 / d) ln [{-(1-R) ² + ((1-R) ⁴ + 4R ² T ² ) ^-1 } / (2R ² T)] ・ ・ ・ (2) where d is the film thickness of the polycrystalline Si film (p-Si), and λ is the wavelength of the laser beam LM.

The extinction coefficient k has a linear relationship, that is, a substantially equivalent relationship with the absorption coefficient α, and is given by the following equation (3), where c is the light velocity and ω is the angular frequency of the laser beam LM. k = (c / 2ω) α ··· (3)

The above equations (1) and (2) are derived from the following equations (4) and (5). R = {(n-1) ² + k ² } / {(n + 1) ² + k ² } ... (4) T = {(1-R) ² exp (-αd)} / {1-R ² exp (-2αd)} (5)

That is, since the reflectance R and the transmittance T are represented by n and k (α) as in the above equations (4) and (5), n
By solving these simultaneous binary equations (4) and (5) for k and (k), the above equations (1) and (2) are derived. Strictly speaking, the above equations (4) and (5) are applied to the case of vertical incidence, but can be applied mutatis mutandis (approximate) to the case of oblique incidence.

The mobility calculator 56 calculates the following equation (6) based on the refractive index n and the absorption coefficient α (extinction coefficient k) obtained by the refractive index / absorption coefficient (extinction coefficient) calculator 54. By calculation, the mobility μ in the polycrystalline Si film (p-Si) on the glass substrate G is obtained. μ = cnα / 4πen _f (6) where e is the electron element content and n _f is the polycrystalline Si film (p−S
i) Free electron density (constant).

The free electron density n _f may be given by the following equation (7). n _f = m _e (w _p ) ² / 4πe ² (7) where m _e is the electron mass and w _p is the plasma frequency.
For example, if the plasma frequency w _p is 0.38 μm (wavelength conversion value), then n _f = 1.13E 20 / cm ³ .

The corrected mobility calculating unit 58 calculates the mobility μ due to the temperature rise of the polycrystalline Si film (p-Si) at the mobility monitoring position P _M due to the incidence of the laser beam LM and thus the change in the free electron density n _f. The error of is corrected or canceled, and the corrected mobility μ _C is obtained by calculating the following formula (8). μ _C = μ−A (E _λ −B) ^3/2 (8) where A is a proportional constant, E _λ is an energy conversion value (constant) of wavelength λ, and B is an offset constant.

E _λ may be given by equation (9) below. E _λ = hc / λ (9) where h is Planck's constant.

As described above, the mobility monitor 34
By performing a predetermined calculation based on the reflected light detection signal S _R from the reflected light receiving unit 38 and the transmitted light detection signal S _T from the transmitted light receiving unit 40 (in particular, the above equations (1), ( 2) and (6) are calculated) to calculate the mobility of the polycrystalline Si film (p-Si) immediately after being formed on the glass substrate G.

The process control unit 44 includes the mobility monitor unit 3
It is inspected whether or not the mobility μ _C calculated in 4 is within a predetermined mobility allowable range, and if it is within the allowable range, it is judged as a non-defective product and the process is passed to the next step. Since the crystallization laser annealing is the final step in this system, the glass substrate G judged as a good product is transferred to the cassette chamber 2 via the transfer chamber 10.
It is sent to any one of 0 and 22. If the mobility μ _C is out of the allowable range, the process control unit 44 appropriately changes the process parameters so that the mobility μ _C falls within the allowable range, and re-executes the crystallization laser annealing step as described above. Let For example, when the mobility μ _C is smaller than the allowable range, parameter control such as increasing the pulse energy of the annealing laser beam LA or decreasing the scanning movement speed of the glass substrate G (slow cooling) may be performed. . On the contrary, when the mobility μ _C is larger than the allowable range, the pulse energy of the annealing laser beam LA may be lowered, or the scanning movement speed of the glass substrate G may be increased (the cooling speed may be increased). .

Even when the crystallization laser annealing is re-executed, the mobility monitor 34 determines the mobility of the polycrystalline Si film (p-Si) re-formed on the glass substrate G by the same mobility monitoring as above. calculate. Then, the process control unit 44 re-inspects the mobility, and when the inspection result is again defective, as long as the cost spent for the crystal grain size control step is less than the cost obtained from the recovery of the glass substrate G, the above procedure May be repeated.

As described above, in this embodiment, the laser annealing apparatus 14, 16 is provided with a mobility monitoring function for calculating the mobility of the polycrystalline Si film in a non-contact manner and in-situ, and the polycrystalline Si film is Since the process of the polycrystalline laser annealing is controlled by feeding back the mobility of C.sub.2, a polycrystalline Si film having a desired crystal grain size can be obtained on the glass substrate G with a high yield. The mobility monitor 34 may be provided outside the laser annealing devices 14 and 16, for example, inside the transfer chamber 10.

Here, the mobility monitor unit 3 of this embodiment is used.
4 above, the above equation for calculating the mobility μ _C ,
In particular, the theory using (6) will be explained. In this embodiment,
As described above, at the mobility monitoring position P _{M, the} polycrystalline S
The i-film (p-Si) is irradiated with the laser beam LM. Since the laser beam LM propagates as an electromagnetic wave in the polycrystalline Si film (p-Si), its electromagnetic wave propagation characteristic is represented by the following formula.
It is represented by Maxwell's equation (cgs unit) like (10). rotH = (4πi + δD / δt) / c (10) However, H is a magnetic field.

The current i and the electric flux density D are represented by the electric field E as in the following equations (11) and (12). i = σE (11) D = εE (12) where σ and ε are the electric conductivity and dielectric constant of the polycrystalline Si film (p-Si).

By substituting the above equations (11) and (12) into the above equation (10) and time-differentiating both sides, the following equation (13) is obtained. ∇ ² E =-(μ _m / c ² ) {4πσ (δE / δt) + ε (δ ² E / δt ² )} (13) However, μ _m is the transparency of the polycrystalline Si film (p-Si). Magnetic susceptibility.

Thus, the dielectric constant ε is included in the above equation (13) derived from the electromagnetic wave propagation characteristics in solid (p-Si).
And the electrical conductivity σ appears.

Strictly speaking, the permittivity ε is a complex permittivity (ε ₁ −i ε ₂ ) as expressed by the following equations (14) and (15), and the complex refractive index n ₋ squared to n ₋ ² equal. Moreover, the complex refractive index n _- square n of _- ² is expressed by the refractive index n and extinction coefficient k as in Equation (16) below. ε = ε ₁ −i ε ₂・ ・ ・ (14) ε = n ₋ ²・ ・ ・ (15) n ₋ ² = (n ² −k ² ) + i ² nk ・ ・ ・ (16)

These relational expressions (14), (15), and (16) are converted into the above equations.
Substituting into (13), the following equation (17) is obtained. ∇ ² E = − (μ _m / c ² ) [4πσ (δE / δt) + {(n ² −k ² ) + 2nki} (δ ² E / δt ² )] (17)

A general solution of E is expressed by the following equation (18).     E = (1 / A) Eoexp [i {ω (t-A / c) + φo}] (18)

When the above equations (17) and (18) are differentiated with respect to time, the iω product per time is attached to E, and the imaginary part of the coefficient is equal on both sides, and the following equation (19) is obtained. 0 = (4πσ (iω) + (2nki) (iω) (iω) ∴ 0 = iω (4πσ-2nkω) ∴σ = 2nkω / 4π (19)

Since the extinction coefficient k and the absorption coefficient α have the relationship of the above expression (3), that is, the relationship of k = (c / 2ω) α, the above expression (19) is expressed by the following expression ( It is equivalent to 20). σ = cnα / 4π (20)

On the other hand, there is a relation of the following equation (21) between the electric conductivity σ and the mobility μ in the solid. σ = en _f μ ‥‥‥ (21)

If σ is eliminated from the above equations (20) and (21),
Equation (6) above is obtained for the mobility μ.

By the way, the optimum wavelength of the light beam used for the mobility monitoring of the present invention as described above varies depending on the material of the semiconductor thin film to be measured. It has been found that the wavelength of the monitoring light beam with respect to the Si film is preferably in the range of 0.2 μm to 0.4 μm, and particularly, around 0.3 μm is most effective.

The graphs shown in FIGS. 4 to 7 are light beams (laser beam L) for mobility monitoring in the present invention.
The optical characteristics and the mobility versus wavelength characteristics obtained when the wavelength of M) is changed within the range of 0.25 μm to 1.0 μm are obtained by simulation.

As shown in the figure, the wavelength of the laser beam LM is
The characteristic values increase as the length becomes shorter than around 0.5 μm.
Change, especially the transmittance T is remarkably reduced and 0.4 μm
From near, it decreases to around 0, while the refractive index n and absorption
The rate (1-R-T) increases and then decreases.
It rises and repeats the maximum and minimum peaks (Fig. 4,
5 and 6). This property is a characteristic of typical dielectric dispersion.
It is thought that this is because the electronic polarization cannot catch up. I
Even if it is displaced, the wavelength is within the range of 0.25 μm to 0.4 μm
Shows a significant mobility monitor value, especially around 0.3 μm
A value close to the actual measured value (about 100 cm²/ Vsec)
Peak values are obtained (Fig. 7). The simulation shown
The shortest wavelength is 0.25 μm, but at least
Also, a significant mobility monitor value was obtained up to around 0.20 μm.
It is thought to be done. In addition, when the wavelength is shortened,
The energy of the laser beam LM changes the free electron density (temperature
Every time) ^3/2Or (1 / wavelength)^3/2Rises rapidly in proportion to
Therefore, the increase in mobility is calculated as shown in equation (8).
Correction value A (E_λ-B)^3/2Canceled by
(Fig. 7). In the illustrated example, A = 7 and B = 2.
It

Next, in this embodiment, a preferable mode of the wavelength of the laser beam LA used for the crystallization laser annealing will be described.

FIG. 8 shows typical transmittance-wavelength characteristics (characteristic of Corning 1737) of the glass substrate for TFT. As is clear from the characteristics of FIG. 8, in the TFT glass substrate, the transmittance shows a saturation value close to 1.0 within the wavelength range of 0.4 μm to 2.5 μm, and is less than 0.4 μm. The transmittance remarkably decreases in the wavelength region longer than 2.5 μm. That is, when the wavelength region of 0.4 μm to 2.5 μm is used, even if the light enters the glass substrate, the light hardly penetrates and is transmitted, so that the glass substrate is not likely to be damaged or deteriorated. On the other hand, as is clear from the data of the emissivity (absorptivity) versus wavelength characteristics shown in FIG. 9, the emissivity (absorptivity) of polycrystalline Si is remarkably reduced in the wavelength region longer than 1.0 μm, and amorphous Si It is considered that the emissivity (absorption rate) of s. Therefore, the laser light LA
In an application in which is likely to pass through the amorphous Si film and enter the glass substrate, it is preferable to select the wavelength of the annealing laser light LA within the range of 0.4 μm to 1.0 μm. It is possible to effectively prevent the glass substrate from being damaged or deteriorated while ensuring the absorption efficiency.

Further, it can be seen from the data of the transmittance versus wavelength characteristic shown in FIG. 10 that molten (liquefied) Si exhibits a good reflectance for a wavelength of 0.4 μm to 1.0 μm.
That is, when the amorphous Si is melted by the laser energy and changed into liquid Si, the reflection of the laser light LA is increased and the amount of transmission to the glass substrate side is decreased. Therefore, it is advantageous for an application in which the vicinity of the surface layer of the film is melted intensively.

From another point of view, in molten (liquefied) Si, the reflectance is remarkably lowered (FIG. 10) and the absorptance is remarkably increased in the vicinity of the plasma frequency or in a wavelength region shorter than the plasma frequency. Therefore, in an application in which it is desired to obtain a molten state fully or surely to the deep layer even after changing from amorphous Si to liquid Si, the wavelength range of the laser light LA is selected in the vicinity of the plasma frequency or in a shorter wavelength range. do it.

Next, a method of applying a magnetic field suitable for crystallization laser annealing in this embodiment will be described.

11 and 12 show a magnetic field application method according to one embodiment. In the embodiment of FIG. 11, the magnet 62 of one polarity, for example, N pole, is provided on the film surface (upper surface) side of the substrate G on the downstream side of the laser irradiation position P _A or in the polycrystalline Si film (p-S).
i) The magnet 64 with the south pole is placed close to the substrate G.
The back surface is disposed at (lower surface) side toward the center or amorphous Si film (p-Si) side of the laser irradiation position P _A, the laser irradiation position P _A magnetic field B formed between the magnets 62 and 64 It is offset to the downstream side or the polycrystalline Si film (p-Si) side. In the embodiment of FIG. 12, a magnet 66 having an N pole and an S pole is provided on the film surface (upper surface) side of the substrate G adjacent to the downstream side of the laser irradiation position P _A or near the polycrystalline Si film (p-Si). The magnetic field formed between the N-pole and the S-pole of the magnet 66 is locally applied near the solidification interface on the polycrystalline Si film (p-Si) side.

Molten Si produced at the laser irradiation position P _A
Area (m-Si) Vortex Q _a by natural convection in the vicinity of the solidification interface in, Q _b is generated, likely grain coarsening of the crystal by eddy Q _a in the vicinity of the interface is inhibited in the recrystallization during the cooling process. Vortex Q of molten Si near such solidification interface
magnetic field having a parallel vector component and the substrate moving direction to eliminate _a is preferable. However, the molten S generated near the solidification interface on the amorphous Si film (a-Si) side
The vortex Q _b of i does not particularly affect the grain _coarsening of the crystal, but is rather desirable for fully melting the deep layer of the film. Therefore, it is preferable that it is not affected by the magnetic field as much as possible.

In this embodiment, a polycrystalline Si film (p-Si) is formed by the magnetic field application method as shown in FIG. 11 or 12.
Applying a strong magnetic field in the vicinity solidification interface side to permit the generation of eddy Q _b to weak magnetic fields in the vicinity of the solidification interface of the amorphous Si film (a-Si) side while suppressing the generation of an eddy Q _a with Therefore, the above-mentioned trade-off requirement can be satisfied at the same time, and the effect of the magnetic field for the melt recrystallization of the Si film can be improved. The magnets 62, 64, 66 may be either permanent magnets or electromagnets.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications and changes can be made within the scope of the technical idea thereof. For example, in the above embodiment, in order to measure the transmission in mobility monitoring, and detecting transmitted light LM _T from the monitoring position P _M by the transmitted light receiving unit 40 provided on the back side of the substrate. However, when the transmittance is low and measurement is difficult, the reflected light LM is analyzed by ellipsometry.
It is also possible to measure reflectance and transmittance from _R alone. Here, the elliptically polarized light analysis method is a method in which linearly polarized light is obliquely incident on a measurement target material (for example, a polycrystalline Si film), and the refractive index n and the extinction coefficient k are calculated from the reflected elliptically polarized light. . Hereinafter, the method of ellipsometry will be described with reference to FIG.

Taking the ratio of E-polarized light and P-polarized light, the following formula (22)
Is guided. E _rp / E _rs = -cos (θ ₁ + θ ₂ ) / cos (θ ₁ + θ ₂ ) ＝ ρexp (iδ) ・ ・ ・ (22) When θ ₁ = 0, -1 = ρexp (iδ) When ρ = 1, δ = π θ ₂ = 0, there is a solution of 1 = ρ exp (iδ) and ρ = 1, δ = 0. Therefore, θ ₁ = θ ₀ and δ = π / 2.

When ρ is calculated using a λ / 2 plate, the above equation (2
From 2), θ ₁ and θ ₂ can be calculated. Therefore, the following equation (23), epsilon ₁ (24) from the complex dielectric constant _{(ε = ε 1 -iε 2)} ,
ε ₂ can be calculated. sin θ ₂ = (ε ₁ / ε ₂ ) ^0.5 sin θ ₁・ ・ ・ (23) cos θ ₂ = [1- (ε ₁ / ε ₂ ) sin ² θ ₁ ] ^0.5 ‥‥(twenty four)

Then, n and k can be calculated from the following equations (25) and (26). n ² = (1 / 2ε ₀ ) [ε ₁ ² + ε ₂ ² ] 0.5 + ε ₁ ] ... (25) k ² = (1 / 2ε ₀ ) [ε ₁ ² + ε ₂ ² ] 0.5-ε ₁ ] (26)

Since the extinction coefficient k and the absorption coefficient α are substantially equivalent to each other according to the above equation (3), the mobility μ can be calculated using the equation (6) as in the above embodiment.

Although the above embodiment relates to the low temperature polycrystalline Si film manufacturing apparatus for TFT-LCD, the mobility calculating method or apparatus of the present invention can be applied to the high temperature polycrystalline Si film process. Further, it can be applied to an application for in-situ monitoring of the mobility of any semiconductor thin film other than the polycrystalline Si film.

[0083]

As described above, according to the mobility calculating method or apparatus of the present invention, it is possible to monitor the mobility of a semiconductor thin film with high accuracy even in process, and it is possible to perform process evaluation or quality control. We can make improvements.

According to the semiconductor manufacturing apparatus of the present invention, since the mobility of the semiconductor thin film is fed back in-process to perform highly accurate process control, the product yield can be improved.

Further, according to the crystallization laser annealing method of the present invention, it is possible to satisfactorily melt and recrystallize the amorphous Si film without damaging the glass substrate, and a highly reliable polycrystalline Si film is obtained. Can be obtained.

Further, according to the crystallization laser annealing method of the present invention, even after the surface of the Si film is melted or liquefied, the laser energy reaches the deep layer so that the entire Si film is sufficiently melted and the film quality is good. It is possible to obtain a good polycrystalline Si film.

Further, according to the crystallization laser annealing method or apparatus of the present invention, the grain coarsening of the polycrystalline Si film can be improved by the efficient magnetic field application method.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a system configuration of a low temperature polycrystalline Si film manufacturing apparatus for a TFT-LCD according to an embodiment of the present invention.

FIG. 2 is a schematic front view schematically showing a main configuration in a laser annealing apparatus and a configuration of a mobility monitor section in the embodiment.

FIG. 3 is a block diagram showing a functional configuration of a mobility calculation unit 42 in the embodiment.

FIG. 4 is a graph showing reflectance and transmittance versus wavelength characteristics of a polycrystalline Si film.

FIG. 5 is a graph showing the refractive index and extinction coefficient versus wavelength characteristics of a polycrystalline Si film.

FIG. 6 is a graph showing absorptance versus wavelength characteristics of a polycrystalline Si film.

FIG. 7 is a graph showing mobility versus wavelength characteristics of a polycrystalline Si film.

FIG. 8 is a graph showing typical transmittance-wavelength characteristics of a TFT glass substrate.

FIG. 9 is a graph showing emissivity (absorptivity) versus wavelength characteristics of a polycrystalline Si film, an amorphous Si film, and a molten Si film.

FIG. 10 is a graph showing reflectance vs. wavelength characteristics of a polycrystalline Si film, an amorphous Si film, and a molten Si film.

FIG. 11 is a diagram showing an example of a magnetic field applying method and apparatus for crystallization laser annealing in the embodiment.

FIG. 12 is a diagram showing an example of a magnetic field applying method and apparatus for crystallization laser annealing in the embodiment.

FIG. 13 is a diagram for explaining a method of ellipsometry in the embodiment.

[Explanation of symbols]

10 Transfer chamber 12 Amorphous SiCVD equipment 14, 16 Laser annealing equipment 26 Laser light source 28 Laser optical system 34 Mobility Monitor 36 Light emitting part 38 Reflected light receiver 40 Transmitted light receiver 42 Mobility calculator 44 Process control unit 62, 64, 66 magnets

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 21/268 H01L 21/268 GT 21/336 29/78 624 29/786 627G (72) Inventor Kawamura Gohei 5-3-6 Akasaka, Minato-ku, Tokyo TBS Broadcasting Center F-term in Tokyo Electron Co., Ltd. (reference) 2G059 AA05 BB16 DD12 DD13 EE01 EE02 EE05 GG01 GG04 GG08 GG10 HH01 HH02 HH03 HH06 JJ11 JJ13 JJ19 MM0101 KK01 KK01 KK01 KK03 BA06 CB12 DH60 5F052 AA02 BB07 DA02 DB02 DB03 JA01 5F110 AA01 AA24 BB01 DD02 DD13 GG02 GG13 GG25 GG45 GG47 PP03 PP05 PP06 PP35

Claims (16)

[Claims] 1. A step of irradiating a semiconductor thin film formed on a substrate with a light beam having a predetermined wavelength to measure the reflectance and the transmittance, and a predetermined arithmetic expression based on the reflectance and the transmittance. A method of calculating mobility for a semiconductor thin film, the method comprising: determining the mobility of the semiconductor thin film. 2. The mobility calculating method for a semiconductor thin film according to claim 1, wherein the arithmetic expression is given by the following expression. μ = cnα / 4πen _f ... where μ is the mobility of the semiconductor thin film, c is the speed of light, and n is
And α are the refractive index and absorption coefficient of the semiconductor thin film, e
Is the electron content, and n _f is the free electron density of the semiconductor thin film. 3. The mobility calculation method for a semiconductor thin film according to claim 2, wherein the refractive index n and the absorption coefficient α are given by the following equations and. n = [(2R + 2) + {(2R + 2) ² -4 (1-R) ² (1+ (αλ / 4π) ² )} ^1/2 ] / (1-R) ‥ α ＝- (1 / d) ln [{-(1-R) ² + ((1-R) ⁴ + 4R ² T ² ) ^-1 } / (2R ² T)] Here, d is the semiconductor thin film. The film thickness, λ, is the wavelength of the light beam. 4. The mobility calculating method for a semiconductor thin film according to claim 1, wherein the free electron density n _f of the semiconductor thin film is given by the following formula. n _f = m _e (w _p ) ² / 4πe ² ... Here, m _e is the electron mass, and w _p is the plasma frequency. 5. The mobility calculating method for a semiconductor thin film according to claim 2, wherein the mobility μ of the semiconductor thin film is corrected by the following formula. μ _C = μ−A (E _λ −B) ^3/2 where μ _C is a value obtained by correcting the mobility μ, A is a proportional constant, E _λ is an energy conversion value of wavelength λ, and B is an offset. It is a constant. 6. The semiconductor thin film is a polycrystalline Si film,
The mobility calculation method for a semiconductor thin film according to claim 1, wherein the wavelength of the light beam is within a range of 0.2 μm to 0.4 μm. 7. The mobility calculating method for a semiconductor thin film according to claim 6, wherein the wavelength of the light beam is in the vicinity of 0.3 μm. 8. A light beam irradiating means for irradiating a semiconductor thin film formed on a substrate with a light beam having a predetermined wavelength, and a reflected light corresponding to the light beam from the semiconductor thin film for receiving a reflectance. Reflectance measuring means for measuring, transmittance measuring means for measuring the transmittance by receiving transmitted light corresponding to the light beam from the semiconductor thin film, and movement of the semiconductor thin film based on the reflectance and the transmittance. A mobility calculation device for a semiconductor thin film, comprising a mobility calculation means for calculating a mobility. 9. The mobility calculating device for a semiconductor thin film according to claim 8, wherein the mobility calculating means calculates the following equation. μ = cnα / 4πen _f ... where μ is the mobility of the semiconductor thin film, c is the speed of light, and n is
And α are the refractive index and absorption coefficient of the semiconductor thin film, e
Is the electron content, and n _f is the free electron density of the semiconductor thin film. 10. The mobility calculating device for a semiconductor thin film according to claim 9, wherein the mobility calculating means calculates the following equation to correct the mobility μ of the semiconductor thin film. μ _C = μ−A (E _λ −B) ^3/2 where μ _C is a value obtained by correcting the mobility μ, A is a proportional constant, E _λ is an energy conversion value of wavelength λ, and B is an offset. It is a constant. 11. A semiconductor thin film forming means for forming a semiconductor thin film on a substrate, a mobility calculating device according to claim 8, which calculates a mobility of the semiconductor thin film, and the mobility. A semiconductor manufacturing apparatus comprising: a process control unit that controls a predetermined process parameter in the semiconductor thin film forming unit according to a mobility obtained from a calculation unit. 12. A crystallization laser annealing method in which a semiconductor thin film formed on a substrate is melted by irradiation with laser light and crystallized in a cooling process to form a polycrystalline Si film, wherein the laser light is in a molten state. A crystallization laser annealing method having a wavelength near or shorter than a wavelength corresponding to a plasma frequency in a semiconductor thin film. 13. A crystallization laser annealing method in which a semiconductor thin film formed on a glass substrate is melted by irradiation with laser light and crystallized in a cooling process to form a polycrystalline Si film, wherein the laser light is 0.4 μm. Crystallization laser annealing method having a wavelength in the range of ˜1.0 μm. 14. A semiconductor thin film formed on a substrate is irradiated with a laser beam having a linear cross-section while applying a magnetic field to melt the laser-irradiated portion of the semiconductor thin film, and the laser-irradiated portion is the laser-irradiated portion. In the crystallization laser annealing method, the substrate is moved relative to the laser light so as to move from one end to the other end on the semiconductor thin film, and the semiconductor thin film is entirely melted and recrystallized. A crystallization laser annealing method in which a relatively strong magnetic field is applied near the boundary between the laser irradiated portion and the recrystallized portion of the thin film and the magnetic field near the boundary between the laser irradiated portion and the laser non-irradiated portion of the semiconductor thin film is weakened. 15. The crystallization laser annealing method according to claim 14, wherein the magnetic field has a vector component parallel to a moving direction of the laser irradiation portion. 16. A laser irradiation means for irradiating a semiconductor thin film formed on a substrate with laser light having a linear cross section, and a laser irradiation portion of the semiconductor thin film for receiving the laser light is on the semiconductor thin film. A scanning means for moving the substrate relative to the laser light so as to move from one end to the other end, and a relatively strong magnetic field near the boundary between the laser irradiation portion and the recrystallization portion of the semiconductor thin film. A crystallization laser annealing device having a magnetic field applying means for applying a weak magnetic field in the vicinity of the boundary between the laser-irradiated portion and the laser-unirradiated portion of the semiconductor thin film.