JP2916452B1 - Evaluation method of crystalline semiconductor thin film and laser annealing apparatus - Google Patents

Abstract

An object of the present invention is to evaluate a crystal state of a p-Si thin film formed on a substrate such as glass by laser annealing, and to provide a laser annealing apparatus which realizes high yield and high throughput. The difference between the light transmittance of a polycrystalline silicon thin film and the light transmittance of an amorphous silicon thin film is measured to detect and evaluate the crystal state of the polycrystalline silicon thin film. A laser annealing device that performs laser annealing on the part again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a crystalline semiconductor thin film by laser annealing a substrate on which a thin film semiconductor device is formed, and a laser annealing apparatus using the same.

[0002]

2. Description of the Related Art In a flat display such as a liquid crystal display device, a thin film transistor (TFT) is used as a thin film semiconductor element.
Some have. In a flat panel display having this TFT, it is necessary to improve the field effect mobility of the electrons of the TFT in each pixel portion in order to realize high definition and high image quality.

In order to improve the field-effect mobility of electrons of a TFT, amorphous silicon (hereinafter referred to as a) is deposited on a glass substrate.
-Si) is referred to as polycrystalline silicon (hereinafter referred to as p-Si).
This is achieved by reforming into a thin film and forming a TFT on the substrate.

There are two methods for modifying an a-Si thin film into a p-Si thin film. One is to modify an a-Si thin film substrate by heating it at a high temperature (800 to 1000 ° C.). One is an excimer laser light (for example, a XeCl laser, a wavelength of 308 nm) which is a light having a high absorptivity for the a-Si thin film.
Irradiation, and melting and crystallizing the a-Si thin film. The former is called a high-temperature p-Si TFT substrate manufacturing method, and the latter is called a low-temperature p-Si TFT substrate manufacturing method.

In the method of producing a high-temperature p-Si TFT substrate, it is necessary to use a heat-resistant glass substrate such as quartz glass because the entire substrate is heated to a high temperature. For this reason, in recent years, a low-temperature p-Si TFT substrate manufacturing method of modifying an a-Si thin film into a p-Si thin film by partial heating has begun to be adopted.

This method is generally called a laser annealing method, and has an advantage that a low-cost glass substrate can be used. The laser annealing method includes (1) a method in which a substrate is intermittently moved, and a laser beam is irradiated every time the substrate is moved to perform annealing. (2) A method in which a substrate is fixed and a laser beam is intermittently moved, and a laser beam is irradiated and annealed every time the laser beam is moved. (3) The above (1)
And (2).

A conventional technique for evaluating the state of a p-Si thin film by laser annealing is disclosed in Japanese Patent Application Laid-Open No. 2-4672.
When an a-Si thin film is irradiated with an annealing laser beam represented by Japanese Patent Application Laid-Open No. HEI 1 (1994) -296015 or the like, the Raman scattering light of the annealing laser beam reflected from the surface of the a-Si thin film is dispersed. And Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 0-5508 discloses a method of detecting a radiation wave generated from a surface in accordance with a melting temperature when a thin film is melted, or another laser as a laser beam for annealing as disclosed in JP-A-1-7612. There is a method of superimposing light, capturing the reflected light, and grasping the laser annealing state.

[0008] In each case, the reflected light from the laser annealing portion is captured and evaluated.
A state at the time when the a-Si thin film is irradiated with the -Si thin film and the a-Si thin film is melted is detected and evaluated by reflected light.

In these methods, although the state when the a-Si thin film is melted can be properly grasped, the final p-type in the process of reforming into an a-Si thin film ⇒ melting ⇒ solidification ⇒ p-Si thin film. No consideration has been given to sufficiently grasping the state of the Si thin film.

Further, in order to use Raman spectroscopy, a spectroscopic device is required, and the evaluation device may be large and expensive. Furthermore, no consideration has been given to a method of reprocessing a laser annealing defect portion of a glass substrate.

[0011]

The state of polycrystalline silicon formation by laser annealing is evaluated for the entire glass substrate or for each required portion, and the glass substrate determined to be rejected is returned to the laser annealing step again. If possible, defective products can be eliminated.

An object of the present invention is to provide an evaluation method capable of evaluating the crystallization state of a p-Si thin film by a simple method.

It is another object of the present invention to provide a laser annealing apparatus capable of shortening a processing time and accurately performing laser annealing of a thin film semiconductor which is annealed by effectively utilizing a laser beam.

[0014]

The gist of the present invention to achieve the above object is as follows.

(1) A method for evaluating a crystalline semiconductor thin film by irradiating light to evaluate a crystal state of a p-Si thin film formed on a substrate, wherein the p-Si thin film is irradiated with light for evaluation. The same as the transmission intensity I ₁ of the irradiation light and the light for evaluation.
Reference light that does not pass through the p-Si thin film with light from the light source
Based on the light transmittance is the ratio of the intensity _{I 2 (I 1 / I 2} ) <br/> under evaluation method of a crystalline semiconductor thin film determines its crystalline state.

[0016]

( 2 ) The transmission intensity I ₁ of the irradiation light is read into an evaluation determination device in which a specific light transmittance I value as a reference for evaluation and a light intensity I ₂ value of the reference light are stored in advance. The present invention is the above-described method for evaluating a crystalline semiconductor thin film, in which the light transmittance (I ₁ / I ₂ ) is calculated, and the calculated light transmittance I is compared with the light transmittance I to determine the crystal state.

( 3 ) p-Si thin film formed on substrate
Of crystalline semiconductor thin film to evaluate the crystal state of
An evaluation method in which the p-Si thin film is irradiated with light for evaluation.
And the transmission intensity I ₁ of the irradiation light is the same as the evaluation light.
Reference light that does not pass through the p-Si thin film with light from the light source
Assuming that the ratio to the intensity I ₂ is the light transmittance (I ₁ / I ₂ ), an evaluation judgment device in which a specific light transmittance I value as an evaluation judgment criterion and the light intensity I ₂ value of the reference light are stored in advance. Then, the transmission intensity I ₁ of the irradiation light is read and the light transmittance (I ₁ /
I ₂ ) is calculated, and this is compared with the light transmittance I to determine the crystalline state of the crystalline semiconductor thin film.

( 4 ) The method for evaluating a crystalline semiconductor thin film, wherein the p-Si thin film is obtained by irradiating a laser beam to an a-Si thin film formed on an insulating substrate and crystallizing the same.

( 5 ) Light transmittance A of a-Si thin film substrate
And a light transmittance B in an optimal state as a p-Si thin film substrate and a difference C between A and B as evaluation criteria ,
This advance stored in advance in the evaluation determining device, is irradiated with light for evaluation p-Si thin film to be evaluated, the transmitted intensity I ₁ of該照Shako, with light from the same light source and the irradiation light p- comparing the difference between the light transmittance II and the light transmittance a calculated Nde write read the evaluation determining device and a light intensity I ₂ of the reference beam which does not transmit Si thin film, and the difference C between the a and B By that p-
The present invention relates to an evaluation method of a crystalline semiconductor thin film for determining a crystal state of a Si thin film.

( 6 ) The method for evaluating a crystalline semiconductor thin film, wherein the light intensity I _{2 of the} reference light is stored in an evaluation determining device in advance.

[0022]

( 7 ) A laser annealing apparatus having an evaluation judging device using the above-described method for evaluating a crystalline semiconductor thin film as an evaluation means, and irradiating an a-Si thin film formed on an insulating substrate with annealing laser light. After the polycrystalline thin film is formed, the polycrystalline thin film is irradiated with light for thin film evaluation and determination, and the transmission state of the irradiated light is measured by a CCD photodiode array, so that the crystal state can be evaluated by the evaluation and determination device. Laser annealing apparatus.

( 8 ) a-S formed on the insulating substrate
The arbitrary position of the laser annealing portion of the i thin film and the evaluation result of the crystal state of the portion are stored in the evaluation determination device so as to correspond to each other, and after the laser annealing step, the arbitrary position of the laser annealing portion is determined. The above-described laser annealing apparatus is configured to perform laser annealing again on the portion when the evaluation and determination apparatus determines that the crystal state is defective.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic principle and embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of an evaluation method for evaluating a p-Si thin film according to the present invention based on light transmission intensity. The p-Si thin film substrate 105 is a light-transmissive insulating substrate made of glass, quartz glass, or the like.
An i thin film is formed.

An evaluation light 102 from a light source 101 composed of a mercury lamp, a halogen lamp, or the like is reflected by a reflecting mirror 103 and condensed by a condensing lens 104.
The light enters the thin film substrate 105. Then, the intensity of the transmitted light 108 that has passed therethrough is measured by the light intensity detector 106 and the power meter 107.

At this time, the crystal state of the p-Si thin film is p-Si thin film.
The present inventors have confirmed that the light transmission intensity differs depending on the size of each crystal grain size of Si, and thus, it is possible to evaluate a p-Si thin film corresponding to the crystal grain size. Can be.

Further, by moving the p-Si thin film substrate 105 in the X and Y directions for measurement, it is possible to evaluate the uniformity of the crystal grain size of the entire substrate. In addition, evaluation light 1
02 can be moved in the X and Y directions to obtain the same effect.

FIG. 2 shows an example of the evaluation of a p-Si thin film based on the light transmittance which is the ratio of the light intensity of the light transmitted through the p-Si thin film substrate 105 to the light intensity not passing through the substrate. .

The evaluation light 102 from the light source 101 is split by the beam splitter 109 so that the light intensity becomes 50% each, and one is transmitted through the p-Si thin film substrate 105 to the light intensity detector 106 and the other is emitted. Is a light intensity detector 112 which is condensed by a condenser lens 110 and serves as a reference light 111
Incident on

The outputs of the light intensity detectors 106 and 112 are input to the power meter 107, and the ratio between the two is calculated, so that the transmittance can be calculated.

FIG. 3 is a graph showing the transmittance characteristics with respect to the above-mentioned transmitted light wavelength. The horizontal axis represents the light wavelength. The curve is the transmittance of the a-Si thin film substrate, and the curve to are the transmittance characteristics when the irradiation energy density P of the laser during laser annealing is changed.

The transmittance of the curved a-Si thin film substrate is lower than the transmittance of the p-Si thin film substrate over the entire measurement wavelength range.
Further, the irradiation energy density P of the curve is set to 320 mJ / c.
When it is larger than m ² , the transmittance T (%) also increases, but it can be seen that the transmittance decreases when the above P in the curve is 460 mJ / cm ² . In particular, it is remarkable near a wavelength of 500 nm.

In general, a p-Si thin film is evaluated by preparing a TFT on a p-Si thin film substrate and evaluating the electric field effect mobility of electrons obtained from its electrical switching characteristics. FIG. 4 shows an example of the field-effect mobility of electrons of the TFT. In addition,
The horizontal axis is the laser irradiation energy density P during laser annealing.

As can be seen from FIG. 4, the electron field-effect mobility (hereinafter, referred to as electron mobility) increases in proportion to the irradiation energy density P, and 8.0 near 400 mJ / cm ^2.
cm ² / Vs. This value is about 100 times the electron mobility of a TFT formed on an a-Si thin film substrate. However, at an irradiation energy density P of 400 mJ / cm ² or more, the electron mobility sharply decreases.
These properties are generally described as follows.

Laser annealing is used to convert a-Si to p-
In the process of being modified into Si, a-Si has a high energy density, and when irradiated with a short-pulse laser beam, only the irradiated portion is melted, and then cooled in a specific crystal direction at a stage where it is naturally cooled. Many crystal grains with
-Si is formed.

By the way, in a place where the irradiation energy density is low, since there is not enough energy to melt a-Si sufficiently, it is cooled immediately, and many Si crystals having a small crystal grain size without crystal growth develop. As a result, a p-Si thin film is formed. The fact that the crystal grain size is small means that
When TFTs are formed on such p-Si, the characteristics of the crystal grains are different from those of the crystal grains, because there are many non-crystallized portions and different portions in different crystal orientations. The boundary acts as a resistor, and the electron mobility is reduced.

On the other hand, if the irradiation energy density is too high, the amorphous a-Si thin film will be formed again without being crystallized in the cooling process because a-Si has a high melting temperature. For this reason, even when the irradiation energy density is too high, the electron mobility will decrease.

As described above, the crystallinity of the p-Si thin film depends on the irradiation energy density P, and accordingly, the electron mobility of the TFT is also affected. That is, the irradiation energy density of the laser for irradiating the a-Si thin film is p-Si
It can be seen that there is an optimum value for maximizing the electron mobility of the TFT formed on the thin film.

The present invention resides in a method for evaluating a p-Si thin film which maximizes the electron mobility of the above-mentioned TFT, which is judged from the transmission intensity and transmittance of light.

FIG. 5 shows the difference between the transmittance of each p-Si thin film substrate and the transmittance of each a-Si thin film substrate in FIG. 3 as a light wavelength on the horizontal axis. From this we can see which p
The -Si thin film substrate also shows a maximum value near the wavelength of 500 nm, and the transmittance difference between the curves (a), (b) and (c) increases as the laser irradiation energy density increases, but the irradiation energy density increases. 460 mJ / cm ² [curve (d)] shows a small value.

In particular, the p-Si thin film substrate laser-annealed at 400 mJ / cm ² in the curve (c) has the largest transmittance difference. This shows that the laser irradiation energy density and the light transmittance of the p-Si thin film substrate are correlated. This indicates that there is also a correlation between the laser irradiation energy density and the electron mobility shown in FIG. In addition, it can be seen that, as an index for evaluating the crystal state of the p-Si thin film substrate, it is more remarkable to use the transmittance difference in FIG. 5 as an index than to use the transmittance in FIG.

FIG. 6 shows the relationship between the transmittance difference and the laser irradiation energy density P using the wavelength of light as a parameter. As a result, the irradiation energy density was 400 mJ / cm ² at each wavelength, and the transmittance difference became maximum, and the wavelength λ
= 500 nm is the largest transmittance difference. 6 and 4, it can be seen that the transmittance difference curve and the electron mobility curve show similarities.

As described above, the values of the light transmission intensity, the transmittance, and the transmittance difference can be used as evaluation indices for the crystal state of the p-Si thin film substrate that has been subjected to the laser annealing. Hereinafter, an embodiment in which a control device and a unit for measuring light transmission intensity are combined will be described.

[0046]

[Embodiment 1] FIG. 7 shows a configuration in which the outputs of the light intensity detectors 106 and 112 are taken into an evaluation judging device 113 instead of the power meter 107 of FIG.

In the evaluation judging device 113, the transmittance I (the characteristic data of FIG. 3 in this embodiment) under the condition where the maximum electron mobility of the TFT is obtained is stored in advance, and this is used as an evaluation judging standard. And

Next, using the reflecting mirror 109 as a total reflecting mirror, the light intensity of the reference beam 111 is taken in and stored in the evaluation judging device 113 via the light intensity detector 112, and the reflecting mirror 109 is removed. The p-Si thin film substrate 105 is irradiated with light, and the light intensity of the transmitted light 108 for substrate evaluation is taken into the evaluation determination device 113 via the light intensity detector 106.

By dividing the two light intensity data of the reference light 111 and the transmitted light for substrate evaluation 108 taken into the evaluation / determination device 113 into the evaluation / determination device 113, p
-Calculate the transmittance of the Si thin film substrate 105. The evaluation and determination device 113 compares the transmittance obtained by the division process with the transmittance of the evaluation determination criterion stored in advance. As a result, the transmittance of the evaluation criterion was ± 10%.
If the difference is within, the crystallization state of the p-Si thin film substrate is determined to be acceptable.

The evaluation of the entire p-Si thin film substrate is performed by sequentially moving the p-Si thin film substrate or sequentially moving the evaluation light, and further, by combining these two. And for the area that does not meet the evaluation criteria,
By calculating the coordinate of the movement amount of the p-Si thin film substrate or the movement amount of the evaluation light, and storing it in the evaluation determination device 113,
Re-laser annealing of only the rejected area is enabled.

According to the present embodiment, a portion of the p-Si thin film substrate that does not meet the determination criteria can be specified, and only that specific portion needs to be re-annealed.
-Si thin film substrate can be obtained.

[Embodiment 2] In Embodiment 1, p-S
The value of the light transmittance I (for example, the characteristic of the curve in FIG. 3) in an optimal state as the i thin film substrate was stored in the evaluation judging device 113, and this was used as the evaluation judging standard.

In this embodiment, not the transmittance but the light transmission intensity in an optimum state as a p-Si thin film substrate
13 is used as an evaluation criterion, and is compared with information from the light intensity detector to determine the first embodiment.
The same effect as described above can be obtained.

[Embodiment 3] The value of the light transmittance I (for example, the characteristic of the curve in FIG. 3) in an optimum state as a p-Si thin-film substrate measured in advance by the evaluation judgment device 113 and the reference light 11
1 is stored, and the p-Si thin film substrate 10 is stored.
5 transmits the transmission intensity information of the transmitted light 108 when the evaluation light is irradiated to the evaluation determination device 1 via the light intensity detector 106.
The p-Si thin film is evaluated by calculating the light transmittance II from the ratio of the value taken in to the value 13 and the light intensity of the reference light 111 and comparing the light transmittance I with the light transmittance II using the light transmittance I as an evaluation criterion. I do.

According to this embodiment, since the light intensity of the reference light 111 is stored in advance in the evaluation determining device 113,
Since only one light intensity detector is required as compared with the first embodiment, the evaluation of the p-Si thin film substrate 105 can be performed more easily.

[Embodiment 4] The light transmittance A of the a-Si thin film substrate (for example, the characteristic of the curve in FIG. 3) before the laser annealing is performed in advance, and the light transmittance I in the optimum state as the p-Si thin film substrate (E.g., the characteristic of the curve in FIG. 3), and the evaluation determination device 11 uses the difference C between the light transmittance A and the light transmittance I (e.g., the characteristic of the curve (c) in FIG.
3 is stored.

Further, the light intensity of the reference light 111 is stored, and the transmission intensity information of the transmitted light 108 when the p-Si thin film substrate is irradiated with the evaluation light is evaluated and evaluated via the light intensity detector 106. The light transmittance II is calculated from the ratio between the value taken into the device 113 and the light intensity of the reference light 111 stored in the evaluation determining device 113.

The difference between the light transmittance II and the light transmittance A is calculated by the evaluation judging device 113.
The p-Si thin film is evaluated by comparing and determining the difference C (for example, the characteristic of the curve (c) in FIG. 4). The method of calculating the difference between the light transmittance II and the light transmittance A by the evaluation determining device 113 and comparing and determining the calculated value with the difference C is apparent from the characteristics of the transmittance difference in FIG. As described above, since the characteristic has the maximum value at a specific wavelength, the accuracy of the evaluation determination can be improved by performing the evaluation determination near the maximum value.

Fifth Embodiment In the first to fourth embodiments, the light source 101 such as a mercury lamp or a halogen lamp was used as the reference light source and the evaluation light source, and the evaluation was performed over the entire wavelength range. FIG. 8 shows a configuration of an evaluation method using light transmission intensity and light transmittance at wavelengths.

As an example, a narrow band-pass filter 114 having a characteristic of transmitting only light of 500 ± 10 nm in the wavelength range shown in FIGS. 3 and 5 is used, and the reference light 116 and the evaluation light 115 only in that wavelength range are used. Detect intensity. As a result, only one point of data needs to be taken into the evaluation determination device 113, and the processing speed required for evaluation determination can be further increased.

[Embodiment 6] Instead of using the narrow band-pass filter 114, a laser light source having a specific oscillation wavelength was used as the reference light source and the evaluation light source 101. An argon ion laser is used as a laser light source.

The argon ion laser is 454.5 to 5
There are 10 laser oscillation lines between 28.7 nm, among which the intensity of the 488 nm and 514.5 nm oscillation lines is strong. Although the oscillation intensity is weaker than this, 496.5 nm and 501.
There is also an oscillation line of 7 nm, and any oscillation line can be used as the reference light source and the evaluation light source 101.

In this embodiment, in particular, the curves and the diagrams in FIG.
Considering that the wavelength showing the maximum value of the curve (c) of FIG. 5 is around 500 nm, an oscillation line of 501.7 nm was used as the reference light source and the evaluation light source 101.

Further, a semiconductor laser can be used instead of the argon ion laser. Depending on the type of semiconductor laser, there are an infrared laser and a visible laser,
As a semiconductor laser for visible light, AlGaIn-based (oscillation wavelength: 600 to 690 nm) and ZnSe-based (laser wavelength: 4
50 to 530 nm). In this embodiment, a ZnSe-based semiconductor laser is selected, and a semiconductor laser having an oscillation wavelength near 510 nm is used as the reference light source and the evaluation light source 101.
Used as

By using the laser light as the reference light and the evaluation light as described above, since the characteristics of the laser such as good directivity of light and high stability of wavelength and output can be utilized, high reliability can be obtained. An assessment can be made. Also,
The same effect can be obtained by using a laser of another system or a laser of another oscillation wavelength.

[Embodiment 7] In each of the above embodiments, a light intensity detector was used as a means for measuring the intensity of the reference light and the evaluation light. In this example, a photodetector having an internal photoelectric effect was used as a means for measuring the light intensity, and these were arranged in a line or a two-dimensional matrix to evaluate a p-Si thin film. An example will be described with reference to FIGS.

In FIG. 9, the evaluation light 102 emitted from the light source 101 is the light reflected by the reflecting mirror 103,
The light passes through a uniform intensity distribution optical system 201 for shaping the light into a rectangular or linear light having a uniform intensity distribution, and irradiates the p-Si thin film substrate 105.

Light 108 transmitted through p-Si thin film substrate 105
Enters the intensity distribution transfer optical system 202. The details of the intensity distribution transfer optical system 202 are shown in FIG. This constitutes a reduction optical system, and the lens 206 and the lens 207 are a relay lens system sharing a focal position. Accordingly, the transmitted light 108 is reduced to the transmitted light 203 at a reduction ratio determined by the ratio of the focal length F1 of the lens 206 to the focal length F2 of the lens 207.

The transmitted light 203 is reduced while maintaining the intensity distribution of the transmitted light 108 because of the relay lens system. The transmitted light 203 is a CCD (C
harge Coupled Device)-Photodiode Array 20
4 is incident.

The CCD photodiode array 2 in FIG.
The optical information incident on B at 04 is the p-Si thin film substrate 105
Is captured as an image of light reflecting the light intensity distribution on the surface A, that is, an image signal. This CCD photodiode array 2
Image signal from the CCD photodiode array 2
The image data is input to the evaluation / determination device 113 via the image signal processing device 205 having the driving function 04.

The light source 101 is an argon ion laser having a wavelength of 501.7 nm, is incident on the uniform intensity distribution optical system 201, and is shaped into a 40 mm × 40 mm square laser beam with a uniform intensity distribution. This laser beam is applied to the p-Si thin film substrate 10
The laser beam 108 radiated and transmitted through the laser beam 5 has an intensity distribution reflecting the crystal state of the p-Si thin film in the irradiation region of the p-Si thin film substrate 105. The laser beam 108 is made incident on an intensity distribution transfer optical system 202 of a relay lens system composed of a lens 206 and a lens 207 to form a laser beam 203 reduced in area to 1/5 (8 mm × 8 mm).

The CCD photodiode array 204 includes one
It is composed of 024 × 1024 CCD photodiode elements, and the size of one element is 9.0 μm × 9.0 μm, which is 9.2 mm × 9.2 mm as a whole.
The transmitted light 2 is applied to the CCD photodiode array 204.
When 03 enters, the transmission intensity of the laser light is measured by 889 × 889 CCD photodiodes.

That is, the A side 4 of the p-Si thin film substrate 105
The image information (intensity distribution information reflecting the crystal state of the p-Si thin film) in the area of 0 mm × 40 mm is converted into the area of 45.0 μm × 45.0 μm (8
89 × 889), and the transmission intensity of the laser beam is measured. The quantity of data at this time is 79032.
The number becomes one and is taken into the evaluation judging device 113 via the image signal processing device 205.

The evaluation / judgment device 113 previously stores (1) a-S at an argon ion laser wavelength of 501.7 nm.
i) the transmittance of the thin film substrate, (2) the difference in transmittance at a wavelength of 501.7 nm in the curve (c) in FIG.
(3) As the light intensity for the reference light, the p-Si thin film substrate 1 shown in FIG.
Image information (790321 pieces of data) of a 40 mm × 40 mm area excluding 05 is stored.

The evaluation determining device 113 first divides the reference light intensity data and the evaluation light intensity data to obtain p−
790 of 40 mm × 40 mm area of Si thin film substrate 105
321 transmittances are calculated. From this transmittance, a-Si
The transmittance of the thin film substrate is subtracted, and 790321 transmittance differences are calculated, and this is compared with the transmittance difference value of the evaluation criterion.

If the difference is within ± 10% with respect to the evaluation criterion, the control method is to judge that the crystallization state of the p-Si thin film substrate is acceptable. Calculate the coordinates of the position on the entire thin film substrate,
It is stored in the evaluation determination device 113. This enables re-laser annealing of only the rejected region.

The above operation is repeated by sequentially moving the p-Si thin film substrate or sequentially moving the evaluation light. For example, the size of one p-Si thin film substrate is 240 mm × 20
If the distance is set to 0 mm, the same operation is performed 30 times, so that all evaluation judgments are completed.

In this embodiment, the evaluation judgment method for each area of 45.0 μm × 45.0 μm has been described. However, the shape of the evaluation laser beam in the uniform intensity distribution optical system 201 and the reduction magnification of the intensity distribution transfer optical system 202 By changing the size and the like of the CCD photodiode array 204, it is possible to make an evaluation judgment for each smaller area.

In this embodiment, the evaluation of the p-Si thin film in a form corresponding to the size of the TFT formed on the p-Si thin film substrate can be performed.
T elements can be created.

By calculating the coordinates of the matrix arrangement positions of the TFT elements on the LCD panel, it is also possible to selectively evaluate and determine only the portion where the TFT elements are formed on the p-Si thin film substrate.

Embodiment 8 In Embodiments 1 to 7, p-Si
The method for evaluating and evaluating a thin film substrate and the evaluation determining apparatus have been described. An embodiment in which these evaluation and determining methods are integrated with a laser annealing apparatus will be described with reference to FIG.

The laser beam 302 oscillated from the argon ion laser 301 passes through the reflecting mirrors 303, 304, and 305, passes through the uniform intensity distribution shaping optical system 310, becomes the beam-shaped evaluation laser beam 311, and passes through the transmission window 312. It enters the vacuum vessel 315. Further, the reflecting mirrors 313 and 314
And enters the p-Si thin film substrate surface 316b installed in the vacuum vessel 315.

The evaluation laser light transmitted through the p-Si thin film substrate surface 316b passes through an image transfer optical system 317 and enters a light intensity detector 318 constituted by a CCD photodiode array.

On the other hand, the excimer laser device 3 for annealing
The laser beam 307 emitted from the laser beam 06 passes through the uniform intensity distribution shaping optical system 308 and becomes the excimer laser beam 309 for annealing which is beam-shaped via the reflecting mirror 305. Then, the light enters the vacuum container 315 through the transmission window 312. Further, similarly to the evaluation laser beam 311, the reflection mirrors 313 and 31 are used.
4, the light enters the a-Si thin film substrate surface 316a provided in the vacuum vessel 315.

The reflecting mirror 314, the image transfer optical system 317, and the light intensity detector 318 are fixed to a drive table, and can be moved by a control device 319 and a drive device 320.

The intensity distribution data input to the light intensity detector 318 constituted by a CCD photodiode array is taken into the evaluation judging device 113 via the image signal processing device 205. The laser output and laser oscillation time of the excimer laser device 306 for annealing are controlled by the control device 319. Further, the control device 319 and the evaluation determination device 113 are linked.

The laser annealing apparatus of the a-Si thin film substrate is constituted as described above, and the specific operation will be described below.

Excimer laser device 306 for annealing
Is a pulse laser oscillator that oscillates a laser beam having a pulse width of several tens of nanometers using a XeCl excimer laser device having a wavelength of 308 nm. Excimer laser light 30 oscillated from this
7 is shaped by the uniform intensity distribution shaping optical system 308, passes through the reflecting mirrors 305, 313, and 314, and has a width of 0.3 mm and a length of 20 on the a-Si thin film substrate surface 316a.
The laser beam 309 is a 0 mm top hat linear beam and has a uniform intensity distribution.

The laser beam 309 is applied to the a-Si thin film substrate surface 316a set in the vacuum vessel 315 by 400 mJ /
When irradiated at a power density of cm ² , the a-Si thin film is melted and crystallized in the course of cooling to form a p-Si thin film.

Next, the control device 319 and the drive device 320
Moves the reflecting mirror 314 in the direction of the arrow 321,
The excimer laser 306 is activated by a command from the control device 319 after moving the laser beam 309 at a position where the width of the laser beam 309 overlaps the width of the previous irradiation by 10%, that is, 0.27 mm. Irradiation. By repeating this series of operations, a-Si
The thin film substrate is modified into a p-Si thin film substrate.

The laser beam 302 oscillated from the argon ion laser (wavelength 501.7 nm) 301 in the course of such an operation is shaped by the intensity distribution shaping optical system 310 through the respective reflecting mirrors 303, 304 and 305, and is annealed. P-Si thin film substrate surface 316b in the same manner as
It is a top-hat type linear beam having a width of 0.3 mm and a length of 200 mm on the surface, and is shaped into an evaluation laser beam 311 having a uniform intensity distribution.

The evaluation laser beam 311 is p-Si 5 steps (0.28 mm × 5 steps = 1.4 mm) backward from the position irradiated with the annealing laser beam 309 with respect to the driving direction 321. 31 modified into thin film
Irradiation is performed on the surface 6b.

In other words, the annealing laser beam 30 which is five times earlier is used.
The light annealed at the position 9 is irradiated, and the transmitted light is incident on the image transfer optical system 317 and then incident on the light intensity detector 318 constituted by a CCD photodiode array.

The image transfer optical system 317 reduces the image reflecting the transmission intensity distribution of 0.3 mm × 200 mm on the surface of the p-Si thin film substrate 316b to 1/6 (0.05 mm × 3
(3.3 mm) and transfer to the light intensity detector 318.

The light intensity detector 318 has the dimensions of one CCD photodiode of 9.0 μm × 9.0 μm and 8 × 307.
Two CCD photodiode arrays are formed, and the overall size is 0.72 mm × 27.648 mm. When the transmitted light enters such a light intensity detector 318, the transmission intensity of the laser light is measured by 6 × 3704 CCD photodiodes.

That is, image information (intensity distribution information reflecting the crystal state of the p-Si thin film) in the area of 0.3 mm × 200 mm on the p-Si thin film substrate surface 316b is transferred to 50.0 μm × 54. The laser light is divided into 0 μm regions (6 × 3704) and the transmission intensity of the laser light is measured. At this time, the data quantity is 2222
The number becomes four and is taken into the evaluation judging device 113 via the image signal processing device 205.

The evaluation / judgment device 113 previously stores (1) a-Si at a wavelength of 501.7 nm of an argon ion laser.
The transmittance of the thin film substrate 316a, (2) the transmittance difference at a wavelength of 501.7 nm (evaluation criterion) of the curve (c) in FIG. 5, (3) the a-Si thin film in FIG. Each data of the image information (22224 pieces of data) in the area of 0.3 mm × 200 mm when the substrate 316 is removed is stored.

The evaluation judging device 113 first divides the reference light intensity data and the evaluation light intensity data to obtain p-
22224 transmittances in a 0.3 mm × 200 mm area of the Si thin film substrate surface 316b are calculated. From this transmittance, a
Subtract the transmittance of the Si thin film substrate to calculate 22224 transmittance differences, and compare this with the transmittance difference value of the evaluation criterion.

If the difference is within ± 10% with respect to the evaluation criterion, the control method determines that the crystallization state of the p-Si thin film substrate surface 316b is acceptable. -The coordinates of the position on the entire surface 316b of the Si thin film substrate are calculated and stored in the evaluation determination device 113.

The image transfer optical system 317 and the light intensity detector 318 are connected to the control
19 and the drive device 320 to move in the movement direction 321 every 0.27 mm step.

Thus, the a-Si thin film substrate surface 316
a is p-Si thin film substrate surface 3 by laser annealing
After completion of a series of steps of evaluation and judgment while reforming to 16b, the coordinate position data of the area that does not satisfy the evaluation judgment criteria stored in the evaluation judgment apparatus 113 is transferred to the control apparatus 319, and the annealing position is transferred to the position. The reflecting mirror 314 is moved via the driving device 320 so that the laser beam is positioned, and the laser beam for annealing 309 is irradiated to perform the annealing again.

If there is a region that does not satisfy a plurality of evaluation criteria, the above steps are sequentially performed. The image transfer optical system 317 and the light intensity detector 318 are also moved, and the evaluation determination is performed again. These are referred to as p-Si thin film substrate surface 31.
Repeat until the entire 6b satisfies the evaluation criteria.

According to this embodiment, the p-Si thin film substrate surface 31
By performing the laser annealing until the entire 6b satisfies the evaluation criteria, a high quality p-Si thin film substrate can be provided.

Conventionally, the quality of a p-Si thin film substrate has been ensured by moving an annealing laser beam and performing an annealing process so that the width of the laser beam overlaps the width of the laser beam previously irradiated by 90%. However, in this embodiment, high quality can be ensured only by wrapping the width of the annealing laser light by 10% with respect to the width previously irradiated, so that the time required for laser annealing can be greatly reduced.

In this embodiment, the reflecting mirror 314, the image transfer optical system 317, and the light intensity detector 318 are moved.
The same effect can be obtained by moving the -Si thin film substrate 316a. Further, the evaluation determination laser beam 311 and the annealing laser beam 309 are superimposed to be positioned on the same optical axis, and the irradiation of the annealing laser beam 309 and the light intensity detector 318 using the evaluation determination laser beam 311 are performed. The same effect as described above can be obtained by providing a difference in the detection start time of the above.

[0106]

According to the present invention, it is possible to evaluate the crystallization state of a p-Si thin film in real time at a very simple and low cost without using a spectroscopic optical system using a special optical method. Is possible.

Further, according to the laser annealing apparatus provided with the above evaluation method, the p-type thin film is formed by laser annealing in parallel with the crystallization step from the a-Si thin film substrate to the p-Si thin film.
The crystallization state of the Si thin film is evaluated, and based on the evaluation result, only the region where the crystallization of the p-Si thin film is insufficient can be laser-annealed again, thereby improving the product yield and improving the throughput. be able to.

Further, since a p-Si thin film substrate having a uniform crystallization state can be manufactured, a TFT element (pixel portion) having high quality and uniform performance can be manufactured, and a liquid crystal having high definition and high image quality can be obtained. It is possible to provide a display panel.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for evaluating and evaluating a p-Si thin film substrate according to the present invention.

FIG. 2 is an explanatory diagram of a method for evaluating and evaluating a p-Si thin film substrate according to the present invention.

FIG. 3 is a graph showing transmittance characteristics of a p-Si thin film substrate with respect to light wavelength.

FIG. 4 is a graph showing electric field effect mobility characteristics of TFT electrons with respect to laser irradiation energy density during laser annealing of a p-Si thin film substrate.

FIG. 5 is a transmittance difference characteristic diagram showing a difference between a transmittance of a p-Si thin film substrate with respect to light wavelength and a transmittance of an a-Si thin film substrate with respect to light wavelength.

FIG. 6 is a graph showing a transmittance difference characteristic with respect to a laser irradiation energy density during laser annealing of a p-Si thin film substrate.

FIG. 7 is an explanatory diagram of an evaluation / determination apparatus using the transmission intensity and transmittance of light of a p-Si thin film substrate according to the present invention.

FIG. 8 is an explanatory diagram of an evaluation / judgment device using transmission intensity and transmittance of a specific wavelength such as a laser beam of a p-Si thin film substrate of the present invention.

FIG. 9 is an explanatory diagram of a method for evaluating and judging a p-Si thin film substrate according to the present invention using a CCD photodiode array element as a means for measuring transmission intensity and transmittance.

FIG. 10 is a detailed sectional view of the intensity distribution transfer optical system of FIG. 9;

FIG. 11 is an explanatory view of a laser annealing apparatus according to the present invention.

[Explanation of symbols]

101: light source, 102: evaluation light, 103: reflecting mirror, 10
4: Condensing lens, 105: p-Si thin film substrate, 106:
Light intensity detector, 107 power meter, 108 transmitted light, 109 beam splitter, 110 condensing lens,
Reference numeral 111: Reference light 112: Light intensity detector 113: Evaluation / determination device 114: Narrow bandpass filter 115
... Evaluation light, 116 ... Reference light, 201 ... Uniform intensity distribution optical system, 202 ... Intensity distribution transfer optical system, 203 ... Transmitted light, 2
04: CCD photodiode array, 205: image signal processing device, 206: transfer lens, 207: transfer lens,
301: argon ion laser, 302: laser beam, 3
03: Reflecting mirror, 304: Reflecting mirror, 305: Reflecting mirror, 30
6 excimer laser device, 307 excimer laser light,
308: uniform intensity distribution shaping optical system, 309: excimer laser beam, 310: uniform intensity distribution shaping optical system, 311: evaluation laser beam, 312: transmission window, 313: reflecting mirror, 31
4 ... Reflection mirror, 315 ... Vacuum container, 316a ... a-Si thin film substrate, 316b ... p-Si thin film substrate, 317 ... Image transfer optical system, 318 ... Light intensity detector, 319 ... Control device,
320: drive device, 321: moving direction, 322: moving direction.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-97219 (JP, A) JP-A 8-236440 (JP, A) JP-A 6-224276 (JP, A) JP-A 4- 179118 (JP, A) JP-A-4-240553 (JP, A) JP-A-10-92763 (JP, A) JP-A 1-250738 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/66 G01N 21/17-21/61

Claims (8)

(57) [Claims] 1. A method for evaluating a crystalline semiconductor thin film by irradiating light to evaluate a crystal state of a polycrystalline silicon thin film formed on a substrate, wherein the polycrystalline silicon thin film is irradiated with light for evaluation. The transmission intensity I ₁ of the irradiation light and the evaluation light
Through the polycrystalline silicon thin film with light from the same light source as
Light transmittance which is a ratio between the light intensity I ₂ of the stomach the reference light (I ₁ / I
_{2. A} method for evaluating a crystalline semiconductor thin film, wherein the crystalline state is determined based on ₂ ) . Wherein the evaluation criteria in which a particular light transmittance I value and the reference light evaluation determining device with previously stored light intensity I ₂ value of the optical read the transmitted intensity I ₁ of the irradiation light The method for evaluating a crystalline semiconductor thin film according to claim 1 , wherein a transmittance (I ₁ / I ₂ ) is calculated and the crystal state is determined by comparing the calculated transmittance with the light transmittance I. 3. 3. A polycrystalline silicon thin film formed on a substrate.
Of crystalline semiconductor thin film to evaluate the crystal state of
An evaluation method, wherein light for evaluation is applied to the polycrystalline silicon thin film.
And the transmission intensity I ₁ of the irradiation light and the evaluation light
Through the polycrystalline silicon thin film with light from the same light source as
The ratio of the reference light intensity to the light intensity I ₂ is defined as the light transmittance (I ₁ / I ₂ ).
Then, the transmission intensity I ₁ of the irradiation light is read into an evaluation determination device in which a specific light transmittance I value as an evaluation determination criterion and the light intensity I ₂ value of the reference light are stored in advance, and the light transmittance (I ₁ / I ₂₎ is calculated and the evaluation method of <br/> crystalline semiconductor thin film characterized by determining the crystalline state by comparing the light transmittance I thereto. Wherein said polycrystalline silicon thin film is a crystalline semiconductor thin film according to any one of claims 1 to 3, which was crystallized by irradiating a laser beam to the amorphous silicon thin film formed on an insulating substrate Evaluation methods. 5. A light transmittance A of an amorphous silicon thin film substrate, a light transmittance B in an optimal state as a polycrystalline silicon thin film substrate, and a difference C between A and B are used as evaluation criteria and evaluated. It is stored in the determination device in advance,
Irradiate the polycrystalline silicon thin film to be evaluated with light for evaluation,
The light transmittance I calculated by reading the transmission intensity I ₁ of the irradiation light and the light intensity I _{2 of the} reference light that does not transmit through the polycrystalline silicon thin film with the light from the same light source as the irradiation light was read into an evaluation / determination apparatus.
The difference between I and the light transmittance A and the difference C between A and B
And evaluating the crystalline state of the polycrystalline silicon thin film by comparing the above conditions. 6. The method for evaluating a crystalline semiconductor thin film according to claim 5 , wherein the light intensity I _{2 of the} reference light is stored in an evaluation determining device in advance. 7. A laser annealing apparatus having an evaluation determination apparatus and evaluation means to evaluate the method of the crystalline semiconductor thin film according to any one of the claims 1 to 6, an amorphous silicon thin film formed on an insulating substrate After forming a polycrystalline thin film by irradiating an annealing laser beam, the polycrystalline thin film is irradiated with light for thin film evaluation determination, and the transmission intensity of the irradiated light is measured by a CCD.
A laser annealing apparatus characterized in that the crystal state thereof can be evaluated by the evaluation determining device by measuring with a photodiode array . 8. A laser annealing step, wherein an arbitrary position of a laser annealing portion of an amorphous silicon thin film formed on the insulating substrate and an evaluation result of a crystal state of the portion are stored in an evaluation judging device so as to correspond to each other. After the end of
The laser annealing apparatus according to claim 7 , wherein the laser annealing section is configured to perform laser annealing again on the crystal state at an arbitrary position of the laser annealing section when the evaluation determining apparatus determines that the crystal state is defective.