JPH0851078A - Optical processing device and method - Google Patents

Abstract

PURPOSE:To enable an optical processing device to output a laser beam constant in irradiation energy or kept in a certain range of irradiation energy monitoring the variation of the laser beam in irradiation energy by a method wherein the refractive index of a thin film modified by irradiation with a laser beam is measured continuously. CONSTITUTION:The refractive index of a crystalline silicon film irradiated with an excimer laser beam is measured through an elipsometry. If the measured refractive index is smaller than a prescribed value, thereafter a laser beam is lessened in irradiation energy. If the refractive index is larger than a prescribed value, a laser beam is enhanced in irradiation energy thereafter. By this setup, a crystalline silicon film having a certain refractive index or so can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention disclosed in this specification relates to a technique for evaluating the treatment effect in various treatment steps using a laser beam. Furthermore, the present invention relates to a technique for relatively evaluating and further controlling the irradiation energy of laser light.

[0002]

2. Description of the Related Art A thin film transistor (referred to as a general TFT) using a polycrystalline silicon thin film is known. This T
The FT is used for various integrated circuits, especially for an active matrix type liquid crystal panel. Also, as an attempt to manufacture this active matrix type liquid crystal panel, development of a "low temperature process" is in progress. This is because by using a low temperature process, a glass substrate which is inexpensive and has a large area and which can be obtained at low cost is used, and the cost of the liquid crystal panel itself is suppressed.

In the above-mentioned low temperature process, whether or not the amorphous silicon film formed on the glass substrate can be crystallized by a temperature process of about 600 ° C. or less, which the glass substrate can withstand, is a major issue. As one of the low temperature processes, an amorphous silicon film is formed on a glass substrate by a plasma CVD method or low pressure heat C
A process is known in which the film is formed by the VD method and the film is irradiated with excimer laser light to be transformed into a crystalline silicon film. In this process, the vicinity of the surface of the silicon film is instantaneously brought into a molten state to crystallize the amorphous silicon film.

The crystalline silicon film crystallized by irradiation with laser light, especially excimer laser light, has the advantage that it is dense and has excellent electrical characteristics. Moreover, there is a feature that thermal damage to the substrate is extremely small. However, the irradiation energy of the excimer laser light is unstable, and it is difficult to always perform irradiation under optimum conditions.

The excimer laser uses a specific gas, makes a gas into an excited state by causing a high-frequency discharge to the gas, and utilizes electromagnetic wave emission when the molecules of the gas change from the excited state to the steady state. It was done. Therefore, if the laser oscillation is continued, the principle problem that the impurities in the gas increase or the gas deteriorates, and the output of the laser light decreases even if the same discharge power is applied. Exists. Generally,
Although the output of the laser light is made constant by using a calibration table, etc., it is not sufficient at present. (For example, it is difficult to calibrate in consideration of contamination in the discharge chamber)

It has been found that when a thin film transistor is manufactured using a crystalline silicon film having crystallinity by irradiation with laser light, the characteristics of the thin film transistor are substantially dependent on the irradiation energy of laser light. Therefore, if the irradiation energy of the laser light can always be made constant or of a desired value, a thin film transistor having predetermined characteristics can be obtained. This is not limited to an example of a thin film transistor, and can be widely applied to a semiconductor device using a process by irradiation with laser light.

As a method for evaluating the annealing effect of laser light irradiation on a semiconductor, for example, Japanese Patent Laid-Open Publication No.
There are techniques described in JP-A 8-15943, JP-A-58-40331, and JP-A-1-16378.

[0008] In these methods, the annealing effect due to laser light irradiation to the semiconductor, especially its crystallinity is measured by Raman spectroscopy, and the predetermined annealing effect is evaluated. However, Raman spectroscopy has the following drawbacks. (1) Poor measurement reproducibility. (2) There is a problem in safety because a high power laser such as an Ar laser is used. (3) The price of the device is high. (4) It takes time to measure.

Further, the flatness of the surface of the film is a major factor that influences the characteristics of the completed thin film transistor, but it is difficult to evaluate the flatness of the film surface by Raman spectroscopy. For the above reasons, the Raman spectroscopy alone cannot sufficiently evaluate the crystalline silicon film forming the thin film transistor having the desired characteristics.

Therefore, in combination with the above-described evaluation method using Raman spectroscopy, the flatness of the film is evaluated by the human eye using an optical microscope or SEM (scanning electron microscope). The current situation.

As described above, at present, in the crystallization process of (A) the amorphous silicon film using the excimer laser light, the optimum irradiation condition of the excimer laser light is experimentally found, and the optimum irradiation condition is always kept. Strive for laser light irradiation. (B) The optimum conditions are determined by evaluating their crystallinity by Raman spectroscopy and visually evaluating their flatness.

However, as described above, the irradiation energy of the excimer laser light easily fluctuates, and it is difficult to control the irradiation energy. Also, the above (B)
As shown in, the evaluation of the effect of laser light irradiation is
Depends on two parameters: crystallinity evaluation by Raman spectroscopy and film flatness evaluation by visual observation, and these two parameters are used to control the gradually changing excimer laser light irradiation power. It is basically a difficult method to do.

[0013]

SUMMARY OF THE INVENTION The present invention aims to solve at least one of the following problems. (1) To provide a technique capable of determining the effect in real time in various treatments such as film quality improvement and annealing using a laser beam. (2) To provide a technique capable of irradiating a laser beam while always controlling to the optimum conditions in the film quality improvement and annealing of the thin film using the laser beam. (3) To provide a technique for easily evaluating the crystallinity of a silicon thin film in the crystallization process of the silicon thin film using laser light. (4) To provide a technique capable of easily evaluating the crystallinity of a silicon thin film and the flatness of its surface in a crystallization process of a silicon thin film using laser light. (5) To provide a technique for controlling the irradiation energy of laser light so that it is always close to a predetermined value. (6) A technique is provided for controlling the irradiation energy of laser light so that the irradiation energy is always within a predetermined range.

[0014]

One of the main constitutions disclosed in the present specification is to irradiate a thin film with laser light or strong light, and a refractive index of the thin film irradiated with the laser light or strong light. And a step of controlling the irradiation energy of the laser light or strong light based on the refractive index and irradiating the thin film or another thin film with laser light or strong light. And

The thin film may be a thin film of amorphous silicon or crystalline silicon which is a semiconductor thin film. The conductivity type of the semiconductor is not particularly limited. Further, as the thin film, an oxide material, a nitride material, a metal material or an organic material can be used. That is, a material that is altered by irradiation with laser light or strong light can be used.

As a substrate on which these thin films are formed, there are a glass substrate which is a substrate having an insulating surface, a quartz substrate, various insulating substrates, a semiconductor substrate on which an insulating film is formed, a conductor substrate, and other insulating films. The formed material can be used.

Examples of laser light include KrF, ArF, and XeCl excimer laser light. Further, as the strong light, light having a required wavelength from ultraviolet light to infrared light can be used. Moreover, the shape of the laser beam can be a practical shape such as a rectangular shape, a linear shape, a dot shape, or a planar shape.

As a method for measuring the refractive index of the thin film, a method using ellipsometry can be mentioned.

As a method of controlling the irradiation energy of laser light or intense light, for example, in the case of excimer laser light, a method of controlling the discharge output can be mentioned. Further, a filter may be used to control the irradiation energy.

The above structure is characterized in that the effect of the laser light irradiation is evaluated by measuring the refractive index of the semiconductor thin film which has been altered by the laser light irradiation. For example, by controlling the irradiation energy of the laser light so that the refractive index always becomes a specific refractive index and repeatedly irradiating the laser light as many times as necessary, it is possible to always obtain a predetermined effect. Alternatively, by setting the refractive index of the semiconductor film irradiated with the laser light to be within a predetermined range, the effect of the irradiation with the laser light can be kept within a certain range.

At this time, the first thin film may be used for measuring the refractive index, and the necessary treatment may be performed from the next thin film. Further, one thin film may be irradiated with laser light a plurality of times. Further, when continuously processing thin films formed on a large number of substrates, some of them are used for the measurement of the refractive index, and the refractive index obtained at all times is kept constant throughout the process. The value may be a value or a value in a certain range.

Another main structure disclosed in the present specification is a first step of irradiating a silicon film crystallized by the action of a metal element that promotes crystallization of silicon with laser light or intense light.
The second step of measuring the refractive index of the silicon film irradiated with the laser beam or the intense light, and the laser beam for the silicon film or another silicon film obtained by the same manufacturing method as the silicon film or A third step of irradiating strong light,
In the third step, the irradiation energy of laser light or intense light is controlled based on the value of the refractive index, which is a light treatment method.

The above structure is characterized in that a film crystallized by the action of an element that promotes crystallization is used as the silicon film irradiated with laser light. Such elements include Ni, Pd, Pt, Cu, Ag, Au, In and S.
One or more elements selected from n, Pb, As and Sb can be used. Especially when Ni is used, a remarkable effect can be obtained. Specifically, an element that promotes crystallization is introduced into the amorphous silicon film, and then heat treatment is performed to crystallize the amorphous silicon film,
A crystalline silicon film can be obtained. This heat treatment can be performed at a temperature lower by 50 ° C. or more as compared with the case where the catalyst element that promotes the crystallization is not introduced, and the heat damage to the substrate (particularly the glass substrate) can be greatly reduced.

As the element that promotes crystallization of the amorphous silicon film, one or more elements selected from VIII group, IIIb group, IVb group, and Vb group elements can be used.

According to another aspect of the invention, the irradiation energy of the laser light or the strong light is controlled based on the means for irradiating the laser light or the strong light and the refractive index of the thin film irradiated with the laser light or the strong light. And means for doing so.

In the above structure, as a means for controlling the irradiation energy of laser light or intense light, for example, a mechanism for controlling the discharge power of excimer laser light can be mentioned.

In the above structure, the irradiation energy of the laser light or the strong light is controlled by controlling the irradiation energy of the laser light or the strong light so that the refractive index of the thin film becomes a predetermined value or a value within a predetermined range. Can be a value close to a predetermined value, or a value within a predetermined range. Further, by repeating the operation, it is possible to gradually approach the value of the predetermined refractive index.

[0028]

The irradiation energy of the laser light can be relatively estimated by measuring the refractive index of the thin film which is altered by the irradiation of the laser light. For example, by adjusting the irradiation energy of the laser light so that the refractive index always has a constant value, it is possible to make the energy of the irradiated laser light always approach a specific value. Therefore, even when the irradiation energy of the laser beam is likely to fluctuate, the value of the irradiation energy can be monitored using the above-mentioned refractive index, and the fluctuation can be minimized. In other words, by constantly measuring the refractive index of the thin film that is altered by laser light irradiation, it is possible to monitor the variation in the irradiation energy value of the laser light. It can be set to a value within. Then, the irradiation energy value of the laser light can be set to a constant value or a value within a fixed range. Further, by utilizing this, the effect of laser light irradiation can be made predetermined.

For example, FIG. 4 shows experimental data showing the relationship between the irradiation energy density of laser light and the refractive index n of the silicon thin film whose crystallinity is promoted by the irradiation of laser light. Here, based on this graph, when the refractive index n of the silicon thin film is larger than a predetermined value, the irradiation energy density of the laser light is increased when the new silicon thin film is irradiated with the laser light next time. Then, the refractive index of this silicon thin film can be brought close to a predetermined value. When the refractive index of the silicon thin film is smaller than a predetermined value, the irradiation energy density of the laser light is reduced when the laser light is irradiated next. Also in this case, the refractive index of the silicon thin film can be brought close to a predetermined value.

Further, the same silicon thin film may be repeatedly irradiated with laser light a plurality of times while measuring the refractive index so as to obtain a predetermined refractive index. However, in order to reduce the crystallinity of the silicon film having advanced crystallinity, it is necessary to irradiate the laser beam with a very strong power to once make it into an amorphous state.

By performing the above operation, a silicon thin film having a certain crystallinity can be obtained even if the irradiation energy density of the laser light fluctuates. This means that the irradiation energy density of the laser light can be controlled so that the irradiation of the laser light can always be performed with a predetermined energy density. And it means that the effect of laser light irradiation can be made constant.

Since the film refractive index can also evaluate the film flatness, it is possible to evaluate the crystallinity and the film flatness at the same time. By utilizing this, it becomes possible to manufacture a thin film transistor having predetermined characteristics.

[0033]

【Example】

Example 1 In this example, the state of a silicon film crystallized by irradiation with excimer laser light (this state is defined as a concept including the crystallinity and flatness of the film) is evaluated. A system and its method are shown.

First, the device will be described. FIG. 1 shows a conceptual diagram of a laser annealing apparatus used in this embodiment.
For most of the device, the platform 1 is located above. The base 1 has a structure that is not affected by external vibration. The laser light is oscillated by the oscillator 2. The laser light oscillated by the oscillator 2 is a KrF excimer laser (wavelength 248n
m, pulse width 25 ns). Of course, other excimer lasers or lasers of other types can be used.

The laser light oscillated by the oscillator 2 is amplified by the amplifier 3 via the total reflection mirrors 5 and 6, and further enters the optical system 4 via the total reflection mirrors 7 and 8. The beam of laser light just before entering the optical system is 3 x 2 cm
It is a rectangle of about ² . Then, by passing through the optical system 4, it is processed into an elongated beam (linear beam) having a length of 10 to 30 cm and a width of 0.1 to 1 cm. This optical system 4
The energy of the laser beam passed through is up to 1000 mJ /
It is a shot.

The laser beam is processed into such an elongated beam in order to improve the processability. That is, the linear beam exits the optical system 4, passes through the total reflection mirror 9, and is irradiated on the sample 11. However, since the width of the beam is longer than the width of the sample, the sample should be moved in one direction. Thus, the entire sample can be irradiated with laser light. Therefore, the sample stage and the driving device 10 have a simple structure and are easy to maintain. In addition, the positioning operation (alignment) when setting the sample is easy.

Stage 1 of sample irradiated with laser light
0 is controlled by a computer and is designed to move at a right angle to a linear laser beam. Further, a heater is built in below the stage 10 so that the sample can be kept at a predetermined temperature when the laser beam is irradiated.

The optical path inside the optical system 4 is shown in FIG. The laser light incident on the optical system 4 passes through the cylindrical concave lens A, the cylindrical convex lens B, and the lateral fly-eye lenses C and D, so that the laser light changes from the Gaussian distribution type to the rectangular distribution. Further, the light passes through the cylindrical convex lenses E and F, and the mirror G (see FIG.
Then, it is focused by a cylindrical lens H (not shown in FIG. 1) via a mirror 9) and is irradiated onto the sample.

FIG. 3 shows a principle diagram of ellipsometry.
Ellipsometry measures the apparent refractive index of the film, and the crystallinity and flatness of the silicon film can be evaluated at the same time by using the refractive index obtained by this ellipsometry.

In ellipsometry, as shown in FIG. 3, polarized light is obliquely incident on the surface of a sample (thin film) to be measured. The polarization state of the polarized light of this incident light changes when it is reflected. This amount of change is related to the thickness and refractive index of the thin film. Therefore, ellipsometry is a method in which the amount of change in polarization is first measured, and then the thickness or refractive index is obtained from the amount of change by analytical calculation. For example, if the thickness of the film is known, the refractive index can be obtained.

Using the invention disclosed in the present specification,
An example of forming a crystalline silicon film on a glass substrate by irradiation with laser light will be described. First, a 10 cm square glass substrate (for example, Corning 7959 glass substrate) is prepared. Then, a silicon oxide film of 2000 Å is formed on this glass substrate by a plasma CVD method using TEOS as a raw material.
To the thickness of. This silicon oxide film functions as a base film that prevents impurities from diffusing into the semiconductor film from the glass substrate side.

Next, an amorphous silicon film (amorphous silicon film) is formed by the plasma CVD method. Although a plasma CVD method is used here, a low pressure thermal CVD method may be used. The thickness of the amorphous silicon film is 500
Å Of course, this thickness may be the required thickness. Next, the substrate is dipped in ammonia-hydrogen peroxide mixture and kept at 70 ° C. for 5 minutes to form an oxide film on the surface of the amorphous silicon film. Further, liquid phase Ni acetate is applied to the surface of the amorphous silicon film by spin coating. The Ni element functions as an element that promotes crystallization when the amorphous silicon film is crystallized.

Next, in a nitrogen atmosphere, the temperature of 450 ° C. is maintained for 1 hour to release hydrogen in the amorphous silicon film. This is because by intentionally forming dangling bonds in the amorphous silicon film, the threshold energy at the time of subsequent crystallization is lowered. Then, the amorphous silicon film is crystallized by performing heat treatment at 550 ° C. for 4 hours in a nitrogen atmosphere. The temperature at the time of crystallization can be set to 550 ° C. because of the action of nickel element.

Thus, a crystalline silicon film can be obtained on the glass substrate. Next, using the apparatus shown in FIG. 1, a KrF excimer laser (wavelength 248 nm, pulse width 25 ns) is irradiated to the crystalline silicon film.
By irradiating with this laser light, the crystallinity can be further enhanced.

The laser beam is shaped into a rectangle using a beam shape conversion lens, and the beam area at the irradiated portion is 1
The size is 25 mm × 1 mm. The sample is placed on the stage 10, and the entire surface of the sample is irradiated by moving the stage at a speed of 2 mm / s. The laser light irradiation conditions, first 200 mJ / cm ^2, and 2-step irradiation 250~350mJ / cm ² and then as the irradiation, the number of pulses to 30 pulses / s. Further, the substrate temperature is kept at 200 ° C. during the laser light irradiation. Irradiation is performed in the atmosphere without any particular atmosphere control.

The irradiation energy density at the second stage of the laser light irradiation is changed within the range of 250 to 350 mJ / cm ² , and the refractive index of the crystalline silicon film in each case is shown in FIG. Ellipsometry (wavelength 12
The result of measurement using a semiconductor laser of 94 nm) is shown in FIG.

The term "refractive index" as used herein refers to the refractive index of a crystalline silicon film formed on a glass substrate measured by ellipsometry. Ellipsometry has the characteristic that if the flatness of the measured film is poor, it will be slightly lower than the actual refractive index of the film. Therefore, the obtained value can be regarded as an apparent refractive index including the flatness of the film. Also,
A low refractive index indicates that the film has high crystallinity. Therefore, the smaller the obtained refractive index, the higher the crystallinity of the film and the poorer the flatness of the film. In the case of a silicon film, the lower limit of the refractive index is about 3.

The meaning of FIG. 4 is shown as follows. That is, it can be said that a film having the required crystallinity and an acceptable flatness exhibits a refractive index within a certain range. In other words, if the crystalline silicon film has a refractive index within a certain range, it can be judged that the crystallinity of the film is at a certain level or more and the flatness thereof is within an allowable range.

It can be seen from FIG. 4 that the refractive index of the crystalline silicon film and the energy density of the irradiated laser light are in a proportional relationship. Of course, as described above, the irradiation energy density of the excimer laser light fluctuates, and the value shown by the horizontal axis in FIG. 4 is considered to be relatively relative to some extent.

The experimental data shown in FIG. 4 is obtained by averaging five points on the film surface. The variation in the measured values among the five points was within 2%. This suggests that both the homogeneity of the film and the measurement accuracy of ellipsometry are good.

Generally, the value of the refractive index measured by ellipsometry tends to decrease as the crystallization progresses and the flatness of the surface is impaired. Utilizing this property, the present inventors have invented the following laser processing method. That is, the refractive index of the crystalline silicon film after being irradiated with the excimer laser light is measured by ellipsometry, and if the refractive index is smaller than a predetermined period, the irradiation energy of the laser light after that is reduced and the refractive index is If it is larger than the predetermined value, the irradiation energy of the laser beam thereafter is increased. By doing so, it is possible to always obtain a crystalline silicon film having a predetermined refractive index value or a value close thereto. Then, even if the absolute value of the irradiation energy of the laser beam changes, it is possible to always obtain a crystalline silicon film having a predetermined crystallinity and an acceptable flatness.

For example, for a crystalline silicon film crystallized by heat treatment using Ni as described above, KrF
When the crystallinity is further increased by irradiating the excimer laser light, the surface deterioration state that does not impair the performance of the thin film transistor obtained by using this crystalline silicon film and the height sufficient to drive the TFT The measurement result has been obtained that the refractive index of the crystalline silicon film having the field effect mobility of 1 is approximately 3.5 or less.

According to the measurement, when the refractive index of the crystalline silicon film after irradiation with laser light is 3.5 or more, the field effect mobility of the thin film transistor using the film is 100 or less, and the refractive index thereof is Is 3.5 or less, it is known that the thin film transistor using the film has a field effect mobility of 100 or more. Therefore, for example, by setting the refractive index of the crystalline silicon film to 3.4,
A crystalline silicon film forming a thin film transistor having a field effect mobility of 100 or more can always be obtained.

However, if the refractive index is too low, the flatness of the film is significantly deteriorated and it becomes unsuitable for use in a thin film transistor. Therefore, the appropriate range is preferably such that the refractive index is in the range of 3.2 to 3.5.

The measurement using ellipsometry described in this embodiment is very simple and highly safe. Also, measurement can be done in an extremely short time (tens of seconds). Therefore, for example, every time one substrate is processed, the refractive index of the crystalline silicon film on the substrate is measured by using ellipsometry, and the irradiation energy density when processing the next substrate based on the measured value. It is possible to always irradiate the laser beam with an energy density having a predetermined absolute value by controlling. Then, it is possible to suppress variations in the effect that occur each time the substrate is processed.
Then, by utilizing this, it is possible to mass-produce semiconductor devices having predetermined characteristics, for example, thin film transistors.

Further, in the present embodiment, the example in which the beam is scanned using the linear laser beam has been described, but the laser beam may be irradiated onto the entire surface of the substrate.

[Embodiment 2] This embodiment shows an example of forming a thin film transistor by using the technique shown in Embodiment 1. FIG. 5 shows a manufacturing process of the thin film transistor of this embodiment. In this embodiment, a glass substrate 501 is used as the substrate. Although not shown on the surface of the glass substrate 501,
A silicon oxide film having a thickness of 2000 liters is formed as a base film.

First, an amorphous silicon film 502 is formed on a glass substrate 501 to a thickness of 500Å by a plasma CVD method or a low pressure thermal CVD method. Next, the surface of the amorphous silicon film is irradiated with UV light in an oxygen atmosphere to clean the surface and form an extremely thin oxide film on the surface. Next, a solution of nickel acetate is applied to form a water film 503.
Then, the spinner 500 is used to spin coat the nickel acetate salt solution and blow off the excess solution.

Next, in an inert atmosphere, 450 ° C., 1
The amorphous silicon film 502 is dehydrogenated by performing heat treatment for a time, and a compound layer of nickel and silicon is formed on the surface of the amorphous silicon film.

Next, at 550 ° C. in an inert atmosphere,
By performing heat treatment for 4 hours, nickel is diffused in the film and crystallization is performed. Thus, the crystalline silicon film 504 is obtained. Then, a KrF excimer laser is irradiated using the apparatus shown in FIG. 1 to further improve the crystallinity of the crystalline silicon film 504.

At this time, the refractive index of the crystalline silicon film is measured by ellipsometry every time one substrate is processed, and if the measured value is larger than a predetermined value (for example, 3.4),
If the set value of the irradiation energy of the laser light is increased and the measured value is smaller than the predetermined value, the set value of the irradiation energy of the laser light is decreased. Then, the next substrate is irradiated with laser light. By doing this,
It is possible to always obtain a crystalline silicon film having a predetermined refractive index or a refractive index close to the predetermined refractive index in a state where the substrate is continuously processed. That is, a crystalline silicon film having a predetermined state (film quality) can be obtained.

FIG. 6 shows a chart of the laser beam irradiation process. 6A to 6C configure the processing for one substrate in (A) to (C). Then, by feeding back the result of (C) to (A), the process for the next substrate is corrected. In this way, it is possible to correct the change in the irradiation energy density of the laser light, which changes gradually as the substrate is continuously processed. And, the variation can be always minimized.

What is shown here is that for each substrate,
This is a method of adjusting the laser light irradiation conditions. For example, every time 5 substrates are processed, the refractive index of the crystalline silicon film on the 5th substrate is measured by ellipsometry, and based on that value, Alternatively, the setting of the irradiation energy density of laser light on the next substrate may be controlled.

In the step shown in FIG. 5B, after the crystalline silicon film 504 is obtained, patterning is performed to form an active layer of a thin film transistor. This active layer is shown in FIG.
No. 507 to 509 of the semiconductor layer.

Then, a silicon oxide film 505 which functions as a gate insulating film is formed to a thickness of 1000 Å by plasma CVD or sputtering. Further, the gate electrode 506 is formed of a metal such as aluminum or a silicon semiconductor heavily doped with impurities imparting one conductivity type. afterwards,
Ion implantation (or plasma doping) of impurities imparting one conductivity type is performed using the gate electrode 506 as a mask to form a source region 507 and a drain region 509. At the same time, a channel formation region 508 is formed.
(Fig. 5 (C))

After that, laser light irradiation is performed for recrystallization of the source and drain regions 507 and 509 which are made amorphous by the bombardment of ions and activation of the implanted impurities. At this time, in order to make the irradiation energy density of the laser light constant, a substrate in the state shown in (B) is separately prepared as a sample, and for example, each time one substrate is processed, the separately prepared sample substrate is prepared. A laser beam is radiated to the sample, and the refractive index of the irradiated region is measured by ellipsometry. Then, based on the measured value, the irradiation condition of the laser light on the next substrate is set.

That is, as shown in FIG. 7, the irradiation condition of the laser light is always controlled based on the refractive index of the silicon film formed on the sample substrate. Specifically, if the refractive index of the sample substrate is larger than a predetermined value, the setting is changed so that the irradiation energy density of the laser light becomes large. Also, if the refractive index of the sample substrate is smaller than the predetermined value,
Change the setting so that the irradiation energy density of the laser light becomes smaller. By doing so, it is possible to correct the variation in the irradiation energy density of the laser light each time one substrate is processed, and bring the value closer to a specific value. As a result, the irradiation energy density of the laser light irradiated on each substrate can be made substantially constant, and the same annealing condition can be always maintained.

Thus, after passing through the state shown in FIG. 5C, an interlayer insulating film 510 is next formed from an insulating material such as silicon oxide or silicon oxide and silicon nitride. Next, a source electrode 511 and a drain electrode 512 are formed through a hole making process. Although not shown, a gate extraction electrode is formed at the same time. Then, in a hydrogen atmosphere, 350 ° C., 1
By performing heat treatment for a time, the dangling bonds in the active layer are neutralized to complete the thin film transistor.

When the structure as in this embodiment is adopted, a thin film transistor can be always manufactured by using a crystalline silicon film close to a specific state, and laser light is always used under a condition close to a specific condition. Since annealing (source / drain annealing) can be performed, a thin film transistor with uniform characteristics can be obtained.

[Embodiment 3] This embodiment relates to a technique for correcting the irradiation condition of laser light in real time. The data shown in FIG. 4 are the refractive index of the crystalline silicon film whose crystallinity is promoted by the KrF excimer laser light (refractive index measured by ellipsometry) and the irradiation energy density (mJ of the laser light irradiated at that time). / Cm ² ). As described above, the irradiation energy density shown in FIG. 4 does not represent the actual energy density of the irradiated laser light.

However, it is understood that the relative relationship between the refractive index of the crystalline silicon film whose crystallinity is promoted and the energy density of the irradiated laser light has a proportional relationship as shown in FIG. . Therefore, by constantly controlling the irradiation energy of the laser light so that the refractive index is a predetermined value, the irradiation energy density can always be a constant value.

Therefore, when it is necessary to irradiate a laser beam with a constant output, an amorphous silicon film (or a crystalline silicon film) for monitoring is additionally prepared, and the laser beam for this amorphous silicon film is prepared. The irradiation energy density of the laser beam can be calibrated when necessary by making it possible to always obtain a constant refractive index in the irradiation.

For example, consider a case where it is necessary to irradiate an object to be irradiated with laser light with a predetermined energy.
In this case, an amorphous silicon film for monitoring is separately prepared, and the crystallization or the refraction index of the crystallization which is promoted by the irradiation of the laser beam is measured for each required step. Then, the irradiation energy of the laser light is changed so that this measured value approaches a predetermined value. Then, it is possible to perform correction (calibration) such that the irradiation energy of the laser light always approaches a specific value. That is, the irradiation energy of the laser light can be kept within a certain range.

The structure as described above can be used for various processing devices using laser light, annealing devices, processing devices, cutting devices, and the like.

[0075]

The effects of various treatments by the irradiation of laser light can be evaluated by measuring the refractive index of a thin film which is altered by the irradiation of laser light. Further, by measuring the refractive index of the thin film that is altered by the irradiation of the laser light, the value of the irradiation energy of the laser light can be relatively evaluated. Then, by utilizing this fact, the irradiation energy of the laser light can be controlled to have a specific value or a value close to the specific value.

By utilizing the invention disclosed in this specification, it becomes possible to obtain annealing by irradiation of laser light with a constant effect. Therefore, for example, in manufacturing a thin film transistor, a thin film transistor having uniform characteristics can be obtained. Further, the crystallinity of the crystalline silicon film used for the thin film transistor and the flatness of the film can be evaluated simultaneously and easily.

The invention disclosed in this specification can be used for manufacturing various semiconductors and controlling the irradiation energy and irradiation power of laser light.

[Brief description of drawings]

FIG. 1 shows an outline of an apparatus for irradiating laser light.

FIG. 2 shows an outline of an optical system arranged in an apparatus for irradiating laser light.

FIG. 3 shows a principle diagram of ellipsometry.

FIG. 4 shows the relationship between the irradiation energy density of laser light and the refractive index of a crystalline silicon film irradiated with laser light.

FIG. 5 shows a manufacturing process of a thin film transistor.

FIG. 6 is a chart showing the steps of forming a crystalline silicon film using laser light.

FIG. 7 is a chart showing an annealing process using laser light in a manufacturing process of a thin film transistor.

[Explanation of symbols]

 1 ... ・ Station 2 ・ ・ ・ Oscillator 5,6 ・ ・ ・ ・ Total reflection mirror 3 ・ ・ ・ ・ Amplifier 7, 8 ・ ・ ・ ・ Total reflection mirror 4 ・ ・ ・ ・ ・-Optical system 9 ...- Total reflection mirror 11-Sample (substrate) 10-Stage and driving device 500-Spinner 501-Glass substrate 502- Amorphous silicon film 503 ... Water film 504 ... Crystalline silicon film 505 ... Gate insulating film (silicon oxide film) 506 ... Gate electrode 507 ... Source region 508・ ・ ・ Channel formation region 509 ・ ・ ・ Drain region 510 ・ ・ ・ ・ Interlayer insulating film 511 ・ ・ ・ ・ Source electrode 512 ・ ・ ・ ・ Drain electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H01L 21/66 C 7514-4M 27/12 R 29/786 21/336

Claims (16)

[Claims] 1. A step of irradiating a thin film with laser light or strong light, a step of measuring a refractive index of the thin film irradiated with the laser light or strong light, and the laser light or strong light based on the refractive index. And a step of irradiating the thin film or another thin film with laser light or strong light by controlling the irradiation energy of the above. 2. The optical processing method according to claim 1, wherein the thin film formed on the substrate is a silicon film. 3. The laser light according to claim 1, wherein K is laser light.
An optical processing method, wherein any one of rF, ArF, and XeCl excimer laser light is used. 4. The optical processing method according to claim 1, wherein ellipsometry is used for measuring the refractive index. 5. The optical processing method according to claim 1, wherein the irradiation energy of the laser light or the intense light is controlled so that the refractive index of the thin film has a predetermined value or a value within a predetermined range. 6. A first step of irradiating a silicon film crystallized by the action of a metal element for promoting crystallization of silicon with laser light or strong light, and a silicon film irradiated with the laser light or strong light. And a third step of irradiating the silicon film or another silicon film obtained by the same manufacturing method as that of the silicon film with laser light or strong light. In the third step, the light treatment method is characterized in that the irradiation energy of the laser light or the strong light is controlled based on the value of the refractive index in the third step. 7. The laser light according to claim 6, wherein K is laser light.
An optical processing method, wherein any one of rF, ArF, and XeCl excimer laser light is used. 8. The optical processing method according to claim 6, wherein the silicon film has a refractive index of 3.5 or less. 9. The optical processing method according to claim 6, wherein ellipsometry is used for measuring the refractive index. 10. The element according to claim 6, wherein the elements promoting crystallization are Ni, Pd, Pt, Cu, Ag, Au and I.
An optical treatment method, wherein one or more elements selected from n, Sn, Pb, As, and Sb are used. 11. The optical treatment according to claim 6, wherein one or more elements selected from Group VIII, IIIb, IVb, and Vb elements are used as an element that promotes crystallization. Method. 12. The optical processing method according to claim 6, wherein the irradiation energy of the laser light or the intense light is controlled so that the refractive index of the thin film has a predetermined value or a value within a predetermined range. 13. A means for irradiating laser light or strong light, and a means for controlling irradiation energy of the laser light or strong light based on a refractive index of a thin film irradiated with the laser light or strong light. An optical processing device having. 14. The means for controlling the irradiation energy of laser light or intense light according to claim 13, wherein the thin film is irradiated with laser light or intense light so that the refractive index of the thin film has a predetermined value or a value within a predetermined range. An optical processing device characterized by controlling energy. 15. A means for irradiating laser light or strong light; a means for controlling irradiation energy of the laser light or strong light based on a refractive index of a thin film irradiated with the laser light or strong light; And a means for repeatedly irradiating a laser beam until the refractive index reaches a predetermined value or a value within a predetermined range. 16. A step of irradiating a thin film with laser light or strong light, and controlling irradiation energy of the laser light or strong light based on a refractive index of the thin film irradiated with the laser light or strong light, and again. A light treatment method comprising: a step of irradiating the thin film with laser light or intense light; and a step of repeatedly irradiating the thin film with laser light until the refractive index reaches a predetermined value or a value within a predetermined range. .